Dual container hydrostatic ventilator

ABSTRACT

In an example, a ventilator includes a first container and a second container in fluidic communication with each other via a liquid. The second container includes a second container space surrounded by the second container and a second liquid surface. A hydrostatic pressure in the second container space results from a pressure differential defined by a difference between the first liquid surface elevation in the first container and the second liquid surface elevation. The second container space increases in size with an increase in the breathing gas supplied from a gas supply line to the second container space. An inhalation line is configured to open to permit a flow of the breathing gas from an inhalation inlet in the second container space to an inhalation outlet outside of the liquid and outside of the second container and coupled to a patient, causing the second container space to decrease in size.

CROSS-REFERENCE TO RELATED APPLICATIONS

The application is a continuation-in-part of U.S. application Ser. No.17/527,904, filed Nov. 16, 2021, entitled INVERTED CONTAINER HYDROSTATICVENTILATOR APPARATUS, which is a continuation of U.S. application Ser.No. 17/244,728, filed Apr. 29, 2021, entitled INVERTED CONTAINERHYDROSTATIC VENTILATOR (now U.S. Pat. No. 11,197,972), which is acontinuation of U.S. application Ser. No. 17/096,479, filed Nov. 12,2020, entitled INVERTED CYLINDER HYDROSTATIC VENTILATOR (now U.S. Pat.No. 11,033,706), which is a nonprovisional of and claims the benefit ofpriority from U.S. Provisional Patent Application No. 63/030,005, filedon May 26, 2020, entitled INVERTED CYLINDER HYDROSTATIC VENTILATOR, theentire disclosures of which are incorporated herein by reference.

STATEMENT OF GOVERNMENT INTEREST

The present invention was made by employees of the United StatesDepartment of Homeland Security in the performance of their officialduties. The U.S. Government has certain rights in this invention.

FIELD

The discussion below relates generally to systems and methods ofproviding mechanical ventilation by moving breathable air into and outof lungs of a patient.

BACKGROUND

A ventilator is a machine that supports breathing by delivering oxygeninto the lungs of an individual and removing carbon dioxide from thebody. It uses positive pressure to deliver air into the lungs of apatient. The patient may exhale the air or the ventilator can do it forthe patient. In a typical system, a mechanical ventilator blows air, orair with increased oxygen, through tubes into the patient's airways. Theair flowing to the patient passes through a humidifier, which warms andmoistens the air. A mask can be used on the patient's mouth and nose todeliver the air. In some cases, an endotracheal tube goes through thepatient's mouth and into the windpipe.

SUMMARY

Embodiments of the present invention are directed to systems and methodsfor providing mechanical ventilation by moving breathable air into andout of lungs. One type of system employs positive pressure to produceventilation.

According to specific embodiments, the positive pressure ventilationsystem is most simply described as a container such as a cylinder withina container such as a cylinder. A larger container is upright, closed atthe bottom and open at the top, and partially filled with water,typically distilled water. A smaller container is inverted, open at thebottom and closed at the top, and immersed in the water bath, trappingair within. Static pressure head can be produced by either introducingmore air into the inner container and holding it stationary, therebypushing the water down and out of its open bottom, or by physicallypushing the inner container downward while leaving the amount of trappedair the same. The concept uses both of these principles to produce asteady and metered airflow (the tidal breath) at a prescribed pressure(via downward force exerted on the inner bucket). The inner containervertically reciprocates between a minimum elevation and a maximumelevation, providing breathing air to the patient; the amount ofvertical travel determines the volume of air delivered. Adjustable PEEP(Positive End-Expiratory Pressure) is provided via variable-depthexhalation tubing placed into the water bath; the deeper the tube's end,the greater the back pressure against which a patient must exhale.

In some embodiments, the ventilation system employs components that canbe fabricated with minimal electronics or no microcontroller, so as tocreate a low-cost ventilator which can be easily reproduced at remotelocations with limited supplies and equipment. Working prototypes havebeen fabricated, for instance, from flat acrylic sheet (“square”cylinders) or assembled from glass vases exhibiting desirable geometry(approximately 3 to 5 inches in diameter and 16 to 20 inches in height).Plastic resistant to UV-C light is desirable as the primary material,although prefabricated cylinders meeting this and the geometricconstraints have been difficult to locate; graduated cylinders rangingfrom 2 to 4 liters are one possibility.

In accordance with an aspect of the present invention, a ventilatorcomprises a first container and a second container containing a liquidand being in fluidic communication with each other via the liquid. Thefirst container has a first liquid surface at a first liquid surfaceelevation of the liquid. The second container has a second liquidsurface at a second liquid surface elevation of the liquid. The secondcontainer includes a second container space surrounded by the secondcontainer and the second liquid surface. A hydrostatic pressure in thesecond container space results from a pressure differential defined by adifference between the first liquid surface elevation and the secondliquid surface elevation. A gas supply line supplies a breathing gas tothe second container space. An inhalation line has an inhalation inletin the second container space and an inhalation outlet outside of theliquid and outside of the second container to provide the breathing gasfrom the second container space to a patient. The second container spaceincreases in size with an increase in the breathing gas supplied fromthe gas supply line to the second container space. The inhalation lineis configured to open to permit a flow of the breathing gas from theinhalation inlet in the second container space to the inhalation outletcoupled to the patient, causing the second container space to decreasein size.

In accordance with another aspect of the invention, a method ofsupporting breathing of a patient comprises: placing a first containerand a second container containing a liquid in fluidic communication witheach other via the liquid, the first container having a first liquidsurface at a first liquid surface elevation of the liquid, the secondcontainer having a second liquid surface at a second liquid surfaceelevation of the liquid, the second container including a secondcontainer space surrounded by the second container and the second liquidsurface, and a hydrostatic pressure in the second container spaceresulting from a pressure differential defined by a difference betweenthe first liquid surface elevation and the second liquid surfaceelevation; supplying a breathing gas via a gas supply line to the secondcontainer space, the second container space increasing in size with anincrease in the breathing gas supplied from the gas supply line to thesecond container space; placing an inhalation line having an inhalationinlet in the second container space and an inhalation outlet outside ofthe liquid and outside of the second container to provide the breathinggas from the second container space to a patient; and opening theinhalation line to permit a flow of the breathing gas from theinhalation inlet in the second container space to the inhalation outletcoupled to the patient, causing the second container space to decreasein size.

In accordance with yet another aspect of this invention, a ventilatorcomprises a first container and a second container containing a liquidand being in fluidic communication with each other via the liquid. Thefirst container has a first liquid surface at a first liquid surfaceelevation of the liquid. The second container has a second liquidsurface at a second liquid surface elevation of the liquid. The secondcontainer includes a second container space surrounded by the secondcontainer and the second liquid surface. A hydrostatic pressure in thesecond container space results from a pressure differential defined by adifference between the first liquid surface elevation and the secondliquid surface elevation. An inhalation line has an inhalation inlet inthe second container space and an inhalation outlet outside of theliquid and outside of the second container to provide a breathing gasfrom the second container space to a patient. The ventilator furthercomprises means for expanding the second container space by directingthe breathing gas from a gas supply line to the second container spaceand contracting the second container space by permitting a flow of thebreathing gas from the inhalation inlet in the second container space tothe inhalation outlet coupled to the patient.

Other features and aspects of various examples and embodiments willbecome apparent to those of ordinary skill in the art from the followingdetailed description which discloses, in conjunction with theaccompanying drawings, examples that explain features in accordance withembodiments. This summary is not intended to identify key or essentialfeatures, nor is it intended to limit the scope of the invention, whichis defined solely by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The attached drawings help explain the embodiments described below.

FIG. 1 shows a schematic view of an inverted cylinder hydrostaticventilator (ICHV) system including an ICHV apparatus.

FIGS. 2A-2H schematically illustrate the operation of an ICHV apparatusaccording to an embodiment.

FIG. 2A shows the ICHV apparatus in an initial charging process fromstartup State 0 in bubble-conditioning mode.

FIG. 2B shows the ICHV apparatus in a charging process with tidal volumeaddition to a ready-to-deliver State 1 in bubble-conditioning mode.

FIG. 2C shows the ICHV apparatus in the ready-to-deliver State 1.

FIG. 2D shows the ICHV apparatus in a breath-delivery process from State1 to a breath-delivered State 2.

FIG. 2E shows the ICHV apparatus in the breath-delivered State 2 readyfor charging in non-conditioning mode.

FIG. 2F shows the ICHV apparatus in a charging-and-expiration processfrom State 2 to State 1 in non-conditioning mode.

FIG. 2G shows the ICHV apparatus in the ready-to-deliver State 1.

FIG. 2H shows the ICHV apparatus in a breath-delivery process from State1 to State 2.

FIG. 3A shows an example of a breath demand mode water switch, forswitching on and off of the inhalation valve for on-demand breathinginstead of mandatory breathing, in a neutral state.

FIG. 3B shows the breath demand mode water switch of FIG. 3A in anactive state.

FIG. 4 is a flow diagram summarizing the process of operating the ICHVapparatus of FIGS. 2A-2H.

FIG. 5 is a schematic view illustrating an example of proximity sensorsin an ICHV apparatus.

FIG. 6 is a schematic view illustrating another example of a proximitysensor in an ICHV apparatus.

FIG. 7 is a schematic view illustrating an example of a heater and a UVlight in an ICHV apparatus.

FIG. 8 schematically illustrates an ICHV apparatus according to anotherembodiment.

FIG. 9 schematically illustrates an ICHV apparatus according to anotherembodiment.

FIG. 10 shows an example of a PEEP tube terminating in its own separatesterilization reservoir with permeable membrane shown near the top ofthe free surface.

FIG. 11 is a modified version of the ICHV apparatus of FIG. 8 showing anexample of a smaller reservoir of water treated with a sterilizingagent, hydraulically separated from the main water bath, for housing thereentrant PEEP tube terminus.

FIG. 12 shows a graph of available tidal volume, added mass, and maximumunit height versus delivery pressure of the ICHV apparatus of FIG. 8 .

FIG. 13 illustrates an example of a controller or computing systemincluding logic.

FIGS. 14A-14G show an example of controller logic for operating an ICHVsystem according to an embodiment of the invention.

FIG. 15 schematically illustrates the operation of a variablehydrostatic pressure ventilator (VHPV) apparatus with states (A)-(E)according to an embodiment employing a stationary inverted innercontainer disposed in an outer container of a liquid.

FIG. 16 is a plot of the hydrostatic pressure over time of the VHPVapparatus of FIG. 15 .

FIG. 17 schematically illustrates the operation of a VHPV apparatus withstates (A)-(E) according to another embodiment employing a stationaryinverted inner container disposed in an outer container of a liquid.

FIG. 18 schematically illustrates the operation of a VHPV apparatus withstates (A)-(E) according to an embodiment employing two separatecontainers connected via a fluid conduit through which a liquid flowstherebetween.

FIG. 19 schematically illustrates the operation of a VHPV apparatus withstates (A)-(F) according to an embodiment employing a movable invertedinner container disposed in an outer container of a liquid and beingbiased by a spring in a direction opposing raising of the elevation ofthe inverted inner container.

FIG. 20 is a plot of the hydrostatic pressure over time of the VHPVapparatus of FIG. 19 .

FIG. 21 schematically illustrates the operation of a VHPV apparatus withstates (A)-(G) according to an embodiment employing a movable invertedinner container disposed in an outer container of a liquid and beingbiased by a spring in a direction opposing lowering of the elevation ofthe inverted inner container.

FIG. 22 is a plot of the hydrostatic pressure over time of the VHPVapparatus of FIG. 21 .

FIG. 23 is a schematic illustration of another embodiment of the VHPVaccording to an embodiment employing multiple inverted inner containersdisposed in an outer container of a liquid.

DETAILED DESCRIPTION

A number of examples or embodiments of the present invention aredescribed, and it should be appreciated that the present inventionprovides many applicable inventive concepts that can be embodied in avariety of ways. The embodiments discussed herein are merelyillustrative of ways to make and use the invention and are not intendedto limit the scope of the invention. Rather, as will be appreciated byone of skill in the art, the teachings and disclosures herein can becombined or rearranged with other portions of this disclosure along withthe knowledge of one of ordinary skill in the art.

The design philosophy according to embodiments of the present inventionis to keep the design, its applied physics, and user interface as simpleand visually intuitive as possible. The design principles take advantageof water's abilities to provide static pressure head, low-tolerancesealing, humidification and warming, and viral decontamination whentreated with ultraviolet (UV) light and/or increased salinity.

In some embodiments, the simplicity and viability of this design conceptis realized. It may be low-tech, but it is highly visual toend-operators and reliable with little need for tight tolerances betweenmoving parts. It merely uses the principles of buoyancy, displacement,and gravity through clever geometric manipulation.

ICHV System and Operation

FIG. 1 shows a schematic view of an inverted cylinder hydrostaticventilator (ICHV) system 100 including an ICHV apparatus 110. The ICHVapparatus 110 is connected to a patient mask 120 to be placed over thepatient's face to deliver breathing air to the patient's lungs. Acontroller 130 may be used to control operation of the ICHV apparatus110 and delivery of breathing air via the mask 120 to the patient.

ICHV Apparatus

FIGS. 2A-2H schematically illustrate the operation of an ICHV apparatusaccording to an embodiment. The ICHV apparatus 200 includes an uprightouter cylinder 202 having a closed bottom and an open top and containinga water bath 204, and an inverted inner cylinder 206 having an openbottom submerged in the water bath 204 of the upright cylinder orupright container 202 and a closed top 208 above the water bath 204. Theinner cylinder 206 is configured to move up and down along guide railsprovided inside the upright cylinder 202. The inner cylinder 206 can berestrained from lateral motion by a variety of sliding supports.Vertical guide rails running parallel to the inner cylinder 206 andconnected via sliprings is one method. In one example, a 3D printed “lidskid” upon which valves, breath demand manometer, controller, and airpump(s) are mounted; lateral motion of the inner cylinder 206 isarrested by a rigid sleeve of slightly larger diameter than the innercylinder's outer diameter and extending approximately 12.5 cm down intothe outer cylinder 202. The sleeve's length inhibits tipping of theinner cylinder 206 while its loose fit minimizes friction, whilerotation about the vertical axis is permitted. Protrusions may extendinward from the outer container wall(s) of the outer cylinder 202providing resistance to lateral motion and rotation of the innercylinder 206 while permitting vertical translation.

The inverted cylinder or inverted container 206 includes a gas volume inan inverted cylinder space 210 trapped by the water bath 204 in theupright cylinder 202, in the inverted cylinder space or invertedcontainer space 210 above an inverted inner cylinder free water surface212. The gas volume in the inverted cylinder space 210 can expand orcontract. Adjustable cylinder weights may be disposed on top of theinverted cylinder 206 to control the pressure in the gas volume, whichis set by selecting an amount of the weights. The open bottom of theinverted container 206 is spaced from the closed bottom of the outercontainer 202 by a variable elevation. The inverted container 206 isconfigured to move upward from a preset minimum elevation position whenthe breathing gas in the inverted container space 210 reaches ahydrostatic delivery pressure and to continue moving upward at thehydrostatic delivery pressure while a volume of the inverted containerspace 210 increases at the hydrostatic delivery pressure, the invertedcontainer 206 being configured to stop moving upward when the invertedcontainer 206 reaches a preset maximum elevation position.

In one embodiment, a maximum volume proximity sensor, such as a maximumvolume lower limit switch, is disposed at a location above the invertedcylinder 206 to control the maximum gas volume. A minimum volumeproximity sensor is disposed at a location below the closed top 208 ofthe inverted cylinder 206 to control the minimum gas volume. Forexample, the minimum volume proximity sensor, such as a minimum volumeupper limit switch, is located along the guide rails. The minimum volumeproximity sensor is tripped (e.g., electrically, magnetically,mechanically, acoustically, or optically) when the inverted cylinder 206drops to a preset minimum height or elevation level and activates theminimum volume proximity sensor (see FIGS. 5 and 6 below).

When gas is introduced into the inverted cylinder space 210 via a gassupply line or tube 220 (e.g., by an air pump 221), the pressureincreases until it is sufficient to expand the gas volume and lift theweight of the inverted cylinder 206 and any weight placed thereon. Thepressure is the hydrostatic delivery pressure. During expansion of thegas volume at the hydrostatic delivery pressure via introduction of moregas, the inverted cylinder 206 moves upward and then stops moving upwardwhen the inverted cylinder 206 reaches a preset maximum elevationposition or level and the maximum volume proximity sensor or maximumelevation sensor is activated. During contraction of the gas volume atthe hydrostatic delivery pressure due to escaping of the gas (via aninhalation tube or patient gas delivery tube 222 as described below),the inverted cylinder 206 sinks downward and then stops moving downwardwhen the minimum volume proximity sensor or minimum elevation sensor isactivated. The proximity sensors can be adjusted to set a variablemaximum gas volume and/or a variable minimum gas volume, the differencebetween the two defining the tidal breath. The proximity sensors may beelectrically activated by electrical contact, magnetically controlledelectrical switches (reed switches), mechanically activated, orultrasonically or optically ranged and activated, for example.

A bubbler bypass valve (one-way) 230 is provided on a bubbler bypassline or tube 232. The bubbler bypass valve 230 may be closed to allowthe breathing gas to be supplied via the gas supply line 220 to a gassupply outlet terminating at a bubbler 234 submerged in the water bath204 if enhanced humidification is desired in a bubble-conditioning mode.The bubbler 234 is disposed at a location below the inverted innercylinder free water surface 212 and at or above the open bottom of theinverted cylinder 206, for the breathing gas or breathable gas to egressand bubble up through the water bath 204 prior to entering the trappedgas volume (i.e., bubble mode), thereby serving as a conditioning gassupply outlet.

An inhalation or inspiratory valve or patient gas delivery valve(one-way) 240 is provided on a patient supply (or patient gas delivery)or inhalation line or tube 222 to supply breathing gas, in an openedposition, from the inhalation inlet 224 disposed in the gas volume ofthe inverted cylinder space 210 to the patient.

When the gas supply operates in a non-conditioning mode where bubblesare not desired, the bubbler bypass valve 230 is opened to direct thebreathing gas through the inhalation line 222, which now serves as thenon-conditioning gas supply line. The breathing gas is flowed directlyvia the line 222 exiting the non-conditioning gas supply outlet 224 tothe inverted cylinder space 210 of the inverted cylinder 206 at thelocation above the inverted inner cylinder water free surface 212,bypassing the bubbler 234 to preclude the formation of bubbles (i.e.,direct injection mode).

The ICHV apparatus 200 is designed to deliver the breathing gas from thegas volume of the inverted cylinder space 210 to the patient at aconstant delivery pressure. The prescribed pressure is the targethydrostatic delivery pressure as determined by the total weight of theinner cylinder 206 and any additional weights placed on the innercylinder 206. When the prescribed pressure (as represented by the outercylinder water height at the outer cylinder free water surface 244 abovethe inner cylinder water height at the inner cylinder free water surface212) is reached, the addition of more breathing gas via the gas supplyline will cause the inner cylinder 206 to buoyantly rise until themaximum elevation is reached and the maximum volume proximity sensor isactivated. The additional volume introduced into the gas volume of therising inner cylinder 206 corresponds to a tidal volume. As such, theheight of the maximum volume proximity sensor such as a maximum volumelower limit switch determines the delivered tidal volume. The tidalvolume is the volume of breathing gas delivered to the patient's lungswith each breath by the ICHV system. Historically, initial tidal volumeswere set at 10 to 15 mL/kg of actual body weight for patients withneuromuscular diseases. It can be adjusted by medical professionals fordifferent patients based on their needs.

An exhalation line or tube 252 has an exhalation inlet to receiveexhaled gas from the patient and an exhalation outlet 256 to release theexhaled gas. An exhalation or expiratory valve (one-way) 250 is providedon the exhalation line 252 to permit exhaled breath of the patient toflow, in an opened position, from the exhalation inlet coupled to thepatient (e.g., via a mask) to the exhalation outlet 256 in the waterbath 204 of the upright cylinder 202. The exhalation line 252 terminatesat the exhalation outlet 256 at a desired elevation which is selectedand fixed for operation at the fixed elevation relative to the closedbottom of the outer container 202, in an annular region 258 between theupright cylinder 202 and the inverted cylinder 206, outside of theinverted cylinder 206. A target hydrostatic backpressure is set by asubmerged depth of the exhalation outlet 256 of the exhalation line 252in the water bath 204, which is the depth measured from the outercontainer liquid level 244 between the inverted inner cylinder 206 andthe upright outer cylinder 202. As such, an adjustable PEEP (PositiveEnd-Expiratory Pressure) is provided via variable-depth exhalationoutlet 256 placed into the water bath 204. The depth can be adjustedbased on the patient's ventilation need as determined by the medicalprofessionals. The depth can further be changed as the patient'sventilation need changes.

An inhalation valve 240 is disposed in the inhalation line 222 and isconfigured to be opened to permit the breathing gas to flow from theinhalation inlet 224 to the inhalation outlet or be closed to block thebreathing gas from flowing from the inhalation inlet 224 to theinhalation outlet. An exhalation valve 250 disposed in the exhalationline 252 and being configured to be opened to permit an exhalation gasto flow from the exhalation inlet to the exhalation outlet 256 or beclosed to block the exhalation gas from flowing from the exhalationinlet to the exhalation outlet 256.

In this embodiment, the inhalation line 222 and the exhalation line 252merge, outside of the outer and inner cylinders 202, 206, at a junction262 into a single patient breathing line 260 coupled to the patient(serving as inhalation line when air flows to the patient or exhalationline when air flows from the patient). The junction 262 is disposeddownstream of the inhalation valve 240 and upstream of the exhalationvalve 250. Disposed between the junction 262 and the patient is amanometer 270 containing a non-toxic electrolytic liquid 274. This is anexample of a breath demand mode water switch for switching on and off ofthe inhalation valve 240 in the inhalation line 222 for on-demandbreathing instead of mandatory breathing. The manometer 270 is disposedbetween the inhalation valve 240 and a breathing line opening 266 of thesingle patient breathing line 260 coupled to the patient, which is theinhalation outlet during inhalation by the patient and the exhalationinlet during exhalation by the patient. Details of its operation areshown in FIGS. 3A-3B and described below.

The bubbler bypass valve 230, inhalation valve 240, and exhalation valve250 may be solenoid valves. Solenoid air valves are relativelylow-pressure valves operated by a signal from a low-voltage relay. Thesethree valves are turned on and off by the controller based on sensorinputs in the on-demand breathing mode. In contrast, in the mandatorybreathing mode, the three valves are all programmed to open and closeautomatically at specific times in the breathing cycle. The ICHVapparatus of FIGS. 2A-2H is capable of operating in the on-demandbreathing mode and the mandatory breathing mode.

There are two hydrostatic pressures of interest in the ICHV apparatus.The first is the delivery pressure of breathing gas delivered from thegas volume in the inverted cylinder space 210 of the inverted cylinder206 to the patient during inhalation. The second is the necessaryexhalation backpressure against which the patient must exhale in orderto avoid collapse of the alveoli in the lungs (also known aspositive-end expiratory pressure, or PEEP). The depth of the exhalationoutlet 256 of the exhalation line 252 determines the amount of PEEP thepatient should experience during exhalation (this backpressure ishydrostatically generated). In contrast, the weight of the innercylinder 206 determines the breathing gas delivery pressure (the moreweight, the higher the delivery pressure). This delivery pressure isimmediately exhibited by the difference in height between the water'sfree surface location 244 at an outer container liquid level within theouter cylinder 202 (the annular space 258 between the inner cylinder 206and the outer cylinder 202) and its free surface 212 within the innercylinder 206 at an inner container liquid level. The inner containerliquid level at the inner cylinder's free surface 212 will always belower than the outer container liquid level of the outer cylinder's freesurface 244 (the height difference corresponds to the hydrostaticdelivery pressure). Delivery pressure and available delivered volumeexhibit an inverse relationship (i.e., at a higher delivered pressure,less gas will be available for delivery, due to the location of theinverted inner cylinder free water surface 212 being limited by thecylinder's open end rim); therefore, the design's geometric limitsshould consider the question as to what the largest volume needs to bedelivered at the highest pressure. A possible embodiment to increasepressure and volume range could be clamping geometrically similarextensions to the open ends of the inner and outer cylinders, allowingbase units to be relatively compact for shipment and less-intensive use,but geometrically expanded for patients requiring more tidal volume,more pressure, or both.

Operation of ICHV Apparatus

FIG. 2A shows the ICHV apparatus in an initial charging process fromstartup State 0 in the bubble-conditioning mode. In this start-up step,the open bottom of the inverted inner cylinder 206 is submerged insidethe water bath 204 of the upright outer cylinder 202 with the gas volumeinside the inverted cylinder space 210 above the inverted cylinder freewater surface 212. The exhalation outlet 256 of the exhalation line 252is submerged in the annular space 258 of the water bath 204 between theinner cylinder 206 and the outer cylinder 202 at a submerged depth orelevation selected to set a target hydrostatic backpressure.

The bubbler bypass valve 230 is closed to direct the supply of thebreathing gas to flow to the inverted cylinder space 210. The inhalationvalve 240 is closed. The exhalation valve 250 is opened so that thepatient is free to exhale into the water bath 204 via the exhalationtube 252 having the exhalation outlet end 256 terminating at a presetdepth based on the prescribed positive end-expiratory pressure (PEEP).The inverted inner cylinder 206 is neutrally buoyant, at its lowestelevation, and ready to be filled with breathing gas. The breathing gasbegins displacing water out of the inverted cylinder 206 and buildingpressure. In this way, the inverted cylinder 206 is prefilled withbreathing gas in the gas volume of the inverted cylinder space 210 toset a delivery pressure (as represented by the outer cylinder waterheight at the outer cylinder free water surface 244 above the innercylinder water height at the inner cylinder free water surface 212). Theinner cylinder 206 is sensed to be at the preset minimum height. Thebreathing gas supply source, an air pump 221 in this case, energizes anddelivers air to the inverted cylinder 206. When running inbubble-conditioning mode, the system delivers gas to the bottom of thewater bath 204 where it passes through the bubbler 234 and ascends intothe inner cylinder 206, making it begin to rise.

FIG. 2B shows the ICHV apparatus in a charging process in thebubble-conditioning mode, with tidal volume addition as the apparatusprogresses to a ready-to-deliver State 1. The air pump 221 continues todeliver air to the inverted cylinder space 210 via the bubbler 234 toform diffused, humidified, and warmed bubbles until the inner cylinder206 has risen to a preset height based on the prescribed tidal volume tobe delivered. The inverted cylinder 206 becomes positively buoyant andrises at constant pressure as breathing gas fills the available gasvolume of the inverted cylinder space 210 to add the tidal volume. Thepatient is still free to exhale into the water bath 204 via theexhalation line 252 with the exhalation outlet 256 at the preset depthbased on the prescribed PEEP.

FIG. 2C shows the ICHV apparatus in the ready-to-deliver State 1. Theinner cylinder 206 achieves its maximum height or elevation and the airsource de-energizes (e.g., by turning off the air pump 221). Forexample, the maximum volume proximity sensor trips upon contact with therisen inverted cylinder 206 and signals the air pump 221 to turn off viathe controller. The prescribed tidal volume is achieved as the closedtop 208 of the inverted inner cylinder 206 (or the weight disposed ontop) contacts the terminal of the maximum volume proximity sensor andcompletes the sensor circuit, signaling the gas supply flow to stop viathe controller. The apparatus is ready to deliver the breathing gas tothe patient.

When a breath is sensed as being demanded (on-demand breathing) or whena first preset timing or time limit is reached (mandatory breathing),the inhalation valve 240 separating the trapped breathing gas supply 210from the patient opens, allowing the gas to escape directly to thepatient. The exhalation valve 250 for the PEEP tube 252 closes at thesame time. For example, if operated in the on-demand breathing mode asopposed to the mandatory breathing mode, the apparatus awaits a patientbreath demand signal, which can be detected, for instance, by a breathdemand pressure or vacuum sensor or an inhalation sensor (e.g.,manometer 270) disposed between the inhalation valve 240 and the patientand sensing a pressure drop and generating a breath demand signal by theinhalation sensor. The apparatus may sense a partial vacuum inhalationdemand from the patient via the breath demand pressure sensor, thecontroller opens the inhalation valve 240, and gas escapes from the gasvolume inside the inverted cylinder space or chamber 210 of the invertedcylinder 206 via the patient supply or inhalation tube 222. The invertedcylinder 206 sinks at constant pressure and velocity due to gravity.

In the on-demand breathing operation, the patient breath demand signalis used to open the inhalation valve 240. Alternatively, in a mandatorybreathing operation, the controller opens the inhalation valve 240 toallow a preset amount of inhalation time for inhalation and closes theinhalation valve 240 to allow a preset amount of exhalation time forexhalation at preset timings.

FIG. 2D shows the ICHV apparatus in a breath-delivery process from State1 to a breath-delivered State 2. The inner cylinder 206 continues tosink lower at constant velocity due to gravity as gas is conveyed to thepatient at the pressure indicated by the vertical disparity between thewater bath's lower free surface 212 within the inner cylinder 206 andupper free surface 244 of the outer cylinder 202. The breathing gasdelivery flow rate is determined mostly by the breathing tube diameterof the inhalation line 222 (and of the patient breathing line 260 beyondthe junction 262) and the pressure drop through the inhalation valve240. When the inner cylinder 206 reaches its minimum height, the processrecycles.

FIG. 2E shows the ICHV apparatus in the breath-delivered State 2 readyfor charging in the non-conditioning mode (as opposed to charging in thebubble-conditioning mode of FIG. 2B). The inverted cylinder 206 hassunken to the minimum elevation, delivering a prescribed amount ofbreathing gas (tidal volume) from the gas volume of the invertedcylinder space 210 to the patient. For example, the minimum volumeproximity sensor, when activated, signals the controller to close theinhalation valve and open the exhalation valve. The exhalationbackpressure (i.e., the PEEP) is hydrostatically provided via the waterin the cylindrical bucket or container 202 and strategic placement ofthe exhalation outlet port 256 of the exhalation line 252 in the watercolumn or bath 204, as discussed above. The exhalation line 252 isopened to permit an exhalation gas flow from the patient through theexhalation inlet to the exhalation outlet 256 disposed in the liquidbetween the inverted container wall and the outer container wall.

The inner cylinder 206 is sensed to be at the preset minimum height.When running in non-conditioning mode, the breathing gas supply source,an air pump 221 in this case, energizes and delivers air via the bubblerbypass valve 230 in an open position with most of the gas arriving viathe tube 222 terminating at the inhalation inlet (which now serves asthe non-conditioning gas supply outlet 224) disposed inside the innercylinder in the inverted cylinder space 210 above the water bath's freesurface 212, causing the inner cylinder 206 to begin to rise. Theinhalation valve 240 is closed. The tube 222 serves as an inhalationline with gas flowing out of the inverted cylinder space 210 and, in thenon-conditioning mode, a gas supply line with gas flowing into theinverted cylinder space 210. Meanwhile, the patient is free to exhaleinto the water bath via the exhalation line 252 with the exhalationoutlet end 256 terminating at the preset depth based on the prescribedpositive end-expiratory pressure (PEEP).

FIG. 2F shows the ICHV apparatus in a charging-and-expiration processfrom State 2 to State 1 in the non-conditioning mode. The air pump 221continues to deliver air via the bubbler bypass valve 240 until theinner cylinder 206 has risen again at the constant pressure to thepreset height based on the prescribed tidal volume to be delivered. Thepatient is still free to exhale into the water bath 204 via theexhalation line 252 with the exhalation outlet 256 terminating at thepreset depth based on the prescribed PEEP. The patient exhales via theexhalation line 252 against the hydrostatic pressure prescribed by thePEEP tube terminal depth of the exhalation outlet 256 submerged in thewater bath 204. The exhalation bubbles rise in the annular space 258around the inverted inner cylinder 206. Humidity in the exhaled breathis reabsorbed into the water bath 204. The gas supply 221 flowsbreathing gas to the inverted cylinder space 210. The breathing gascauses the inverted cylinder 206 to rise at constant pressure again. Theinner cylinder 206 charges during expiratory gesture.

FIG. 2G shows the ICHV apparatus in the ready-to-deliver State 1. Theinner cylinder 206 again achieves its maximum height and the air source221 de-energizes. The inner cylinder 206 again (similar to FIG. 2C)achieves its maximum height or elevation and the air source de-energizes(e.g., by turning off the air pump 221). Tidal volume is added and thenbreathing gas delivery to the patient is ready to begin as the patientconcludes the expiratory gesture. When a breath is sensed as beingdemanded (on-demand breathing) or a second preset timing or time limitis reached (mandatory breathing), the inhalation valve 240 separatingthe trapped breathing gas supply 210 from the patient opens, allowingthe gas to escape directly to the patient. The exhalation valve 250 forthe PEEP tube 252 closes at the same time.

FIG. 2H shows the ICHV apparatus in a breath-delivery process from State1 to State 2. Similar to FIG. 2D, the inner cylinder 206 continues tosink lower as gas is conveyed to the patient at the pressure indicatedby the vertical disparity between the water bath's lower free surface212 within the inner cylinder 206 and upper free surface 244 of theouter cylinder 202. When the inner cylinder 206 reaches its minimumheight, the process recycles.

FIG. 3A shows an example of a breath demand mode water switch forswitching on and off of the inhalation valve 240 in the patientbreathing line 260 for on-demand breathing instead of mandatorybreathing. It uses a non-toxic electrolytic liquid (e.g., saltwater) 314in a manometer 310 connected to the patient breathing line 260 (or theinhalation tube or patient supply tube 222 if the exhalation line 252 iscompletely separate from the inhalation line 222 without merging) tocomplete the circuit of an electrical sensor (with sensor line 330 andsensing wire 340 as described below) when a patient begins to inhale.The manometer 310 is disposed between the inhalation valve 240 and theinhalation outlet 266 connected to the patient. The (small) partialvacuum caused by the initial inspiratory gesture closes the circuitbetween the energized terminal and sensor terminal, which tells themicrocontroller to open the inhalation valve 240 to pressurize thepatient breathing line 260 with breathing gas. The switch is reliableand easy to fabricate. It also provides secondary protection againstover-pressurization of the patient breathing line 260 by setting themanometer open end 320 at some prescribed height.

In the neutral state as illustrated in FIG. 3A, an insulated sensingwire 340 terminates with an electrically uninsulated terminal 342slightly above the free surface of an electrolytic solution 314 trappedin the U-manometer 310. Another wire, sensor line 330 at a definedreference voltage, terminates with its electrically uninsulated end 332submerged in the solution 314. The electrical circuit is broken as longas the electrolytic solution 314 is not in contact with both terminals332, 342 simultaneously. The inspiratory valve 240 separating thepatient from the trapped breathing gas supply 210 is closed. Thenormally grounded sensor line 330 communicates with the inhalation valve240 via the microcontroller and relay. When no breath is demanded, thecircuit is broken and the demand signal is negative (LOW). The sensorline 330 extends from the inhalation valve 240 to the electricallyuninsulated end 332 at the bottom of the electrolytic solution manometertubing 310. A low-voltage (e.g., 5 VDC) signal source is coupled to thesensing wire 340 which terminates with the electrically uninsulatedterminal 342 just above the electrolytic solution free surface when thesystem is in the neutral position. The live end 342 of the circuit isexposed but not in contact with the electrolytic solution when no breathis demanded. The height of the open end 320 of the electrolytic solutiontube 310 provides a secondary safety feature preventing overpressuredelivery.

In the active state as illustrated in FIG. 3B, the sensor line 330communicates with the inhalation valve 240 via the microcontroller andrelay. When a slight drop in pressure occurs due to the onset of abreath demand by an inhaling patient, the solution 314 within themanometer 310 shifts toward the exposed sensing wire's bare terminal 342and the breath demand signal is positive (HIGH). A momentary suctionsubsides when the inhalation valve 240 opens and pressurizes thebreathing line 260 to the patient. The live end 342 of the circuit isnow exposed to the electrolytic solution 314 when a breath is demandedcausing a partial vacuum 350 in the manometer 310, causing the liquid314 to migrate upward via the partial vacuum 350. When the solution 314rises enough to submerge both terminals 332, 342, the electrical circuitis completed and the controller senses a demand signal. The controllerresponds by opening the inspiratory valve 240 and closing the expiratory(PEEP) valve (250 in FIGS. 3A-3H).

ICHV Process

FIG. 4 is a flow diagram summarizing the process 400 of operating theICHV apparatus of FIGS. 2A-2H. The apparatus is in the startup stateshown in FIG. 2A and described above. The minimum elevation sensorregisters that the inner cylinder 206 is at the minimum elevation. Inthe preparation step 404 prior to charging, the inhalation valve 240 isclosed and the exhalation valve 250 is opened. Next, the user oroperator specifies (manually or via the controller) whether chargingwill include bubbles (step 408). If bubbles are included in thebubble-conditioning mode, the charging step 412 closes the bubblerbypass valve 230 and starts the air pump 221. The breathing gas supplyflow is directed into the gas volume of the inverted cylinder space 210via the bubbler 234 to achieve the target hydrostatic delivery pressurein the gas volume and lift the elevation of the inner cylinder 206. Ifbubbles are not included in the non-conditioning mode, the charging step414 opens the bubbler bypass valve 230 and starts the air pump 221 todirect breathing gas into the gas volume of the inverted cylinder space210 via the non-conditioning gas supply line 222.

In ready-to-deliver step 420, upon detection that the inner cylinder 206has reached a preset maximum elevation (e.g., by the maximum volumeproximity sensor or maximum elevation sensor), the breathing gas supplyflow into the gas volume is closed (e.g., by deenergizing the air pump221). If the bubbler bypass valve 230 was opened (in thenon-conditioning mode), it is now closed. Next the operator specifies(manually or via the controller) whether the delivery mode is mandatoryor on-demand (step 424).

For mandatory delivery, the next step 430 is to determine whether thefirst prescribed or preset timing has been reached. If not, the systemwaits until the first preset timing is reached (step 432). When thefirst preset timing is reached, a breath-delivery step 440 opens theinhalation line 222 (e.g., by opening the inhalation valve 240) to flowbreathing gas from the gas volume in the inverted cylinder space 210 tothe patient at the target hydrostatic delivery pressure, lowering theelevation of the inner cylinder 206 due to lost buoyancy resulting insinkage. The exhalation valve 250 for the PEEP tube 252 closes at thesame time.

For on-demand delivery, the next step 450 is to determine whether thereis patient breath demand. Upon detection of a patient breath demandsignal, for instance, by a breath demand pressure or vacuum sensor(e.g., manometer 270), the breath-delivery step 440 opens the inhalationline 222 to flow breathing gas to the patient and closing the exhalationvalve 250.

The process returns to step 404, which is now a charging-and-expirationstep, upon detection that the inner cylinder has reached a presetminimum elevation (breath delivered, e.g., by the minimum volumeproximity sensor). The inhalation valve 240 is closed and the exhalationvalve 250 is opened.

ICHV Apparatus—Additional Features and Other Embodiments

FIG. 5 is a schematic view illustrating an example of proximity sensorsin an ICHV apparatus. The proximity sensors 500 include a conductivelayer 502 attached to the closed top of the inverted inner cylinder 506(e.g., by adhesion). A reference voltage line 510 is disposed at anupper elevation and a lower elevation. An upper sensing wire 520 isdisposed at the upper elevation (which represents the maximum volumeproximity) and a lower sensing wire 530 is disposed at the lowerelevation (which represents the minimum volume proximity). The referencevoltage line 510, upper sensing wire 520 and the lower sensing wire 530are connected to a controller 540.

The maximum volume proximity sensor or maximum elevation sensor isformed by an exposed disconnected terminal of the reference voltage line510 and an exposed disconnected terminal of the upper sensing wire 520at the upper elevation. When the conductive layer 502 attached to theinner cylinder 506 simultaneously contacts both terminals, the uppersensing wire 520 adopts the reference voltage and the controller 540sense the cylinder's location at the maximum volume proximity level.

The minimum volume proximity sensor or minimum elevation sensor isformed by an exposed disconnected terminal of the reference voltage line510 and an exposed disconnected terminal of the lower sensing wire 530at the lower elevation. When the conductive layer 502 attached to theinner cylinder 506 simultaneously contacts both terminals, the lowersensing wire 530 adopts the reference voltage and the controller 540senses the cylinder's location at the minimum volume proximity level.

FIG. 6 is a schematic view illustrating another example of a proximitysensor in an ICHV apparatus. An ultrasonic ranging sensor 610 ispositioned directly above and pointed toward the closed top of theinverted inner cylinder 606 to serve as the proximity sensor. Theultrasonic sensor 610 is coupled to a controller 620. Other embodimentsinclude magnetic reed switches or an optical ranging sensor positioneddirectly above and pointed toward the closed top of the inner cylinder606.

FIG. 7 is a schematic view illustrating an example of a heater and a UVlight in an ICHV apparatus. A heating element 710 such as a thermostaticheater or an electric resistance heater is provided inside the outerupright cylinder 702, to heat the water bath 704 in which the innerinverted cylinder 706 is partially submerged, to compensate for theabsence of biologically available heating via sinus cavities. Anultraviolet (UV) light 720 is provided inside the upright cylinder 702to perform virus decontamination and prevent algal and bacterial growth.In other embodiments, the heating element and/or UV light may bedisposed outside the water bath 704. In some embodiments, the UV lightkills pathogens; alternatively, increased salinity in the water bath canbe used.

FIG. 8 schematically illustrates an ICHV apparatus according to anotherembodiment. The ICHV apparatus 800 is similar to the ICHV apparatus 200of FIGS. 2A-2H, including the following similar components: an uprightouter cylinder 802 containing a water bath 804, an inverted innercylinder 806 having a closed top 808, a gas volume in an invertedcylinder space 810 trapped by the water bath 804 in the upright cylinder802 above an inverted inner cylinder free water surface 812, a gassupply line or tube 820, a bubbler bypass valve (one-way) 830 providedon a bubbler bypass line or tube 832, a bubbler 834, an inhalation orinspiratory valve or patient gas delivery valve (one-way) 840 providedon a patient supply (or patient gas delivery) or inhalation line or tube822 with an inhalation outlet to supply breathing gas, an exhalation orexpiratory valve (one-way) 850 provided on an exhalation line or tube852 to permit exhaled breath of the patient to flow, in an openedposition, from an exhalation inlet coupled to the patient (e.g., via amask) to an exhalation outlet 856 in the water bath 804 of the uprightcylinder 802, an annular region 858 between the upright cylinder 802 andthe inverted cylinder 806. The inhalation line 822 and the exhalationline 852 merge at a junction 862 into a single patient breathing line860 coupled to the patient. Disposed between the junction 862 and theexhalation valve 850 is a manometer 870 containing a non-toxicelectrolytic liquid 874. The single patient breathing line 860 leads toa breathing line opening 866 coupled to the patient, which is theinhalation outlet during inhalation by the patient and the exhalationinlet during exhalation by the patient. The inner cylinder's freesurface 812 will always be lower than the outer cylinder's free surface844 (the height difference corresponds to the hydrostatic deliverypressure).

The main difference between the ICHV apparatus 200 of FIGS. 2A-2H andthe ICHV apparatus 800 of FIG. 8 is the presence of a gas supply valve880 in the gas supply line 820 and the absence of the air pump 221 inthe ICHV apparatus 800. As such, instead of controlling the gas supplyflow by controlling the air pump 221 in the ICHV apparatus 200, the ICHVapparatus 800 controls the gas supply flow by controlling the gas supplyvalve 880, which may also be a solenoid valve. Other than this specificfeature, the operation of the ICHV apparatus 800 is substantiallyidentical to the operation of the ICHV apparatus 200.

FIG. 9 schematically illustrates an ICHV apparatus according to anotherembodiment. The ICHV apparatus 900 has many features that are similar tothose in the ICHV apparatus 800 of FIG. 8 , including the followingsimilar components: an upright outer cylinder 902 containing a waterbath 904, an inverted inner cylinder 906 having a closed top 908, a gasvolume in an inverted cylinder space 910 trapped by the water bath 904in the upright cylinder 902 above an inverted inner cylinder free watersurface 912, a gas supply line or tube 920 leading to a bubbler 934disposed in the water bath 904, a gas supply valve (one-way) 980provided on the gas supply line 920, an inhalation or inspiratory valveor patient gas delivery valve (one-way) 940 provided on a patient supply(or patient gas delivery) or inhalation line or tube 922 with aninhalation outlet 924 to supply breathing gas, an exhalation orexpiratory valve (one-way) 950 provided on an exhalation line or tube952 to permit exhaled breath of the patient to flow, in an openedposition, from an exhalation inlet coupled to the patient (e.g., via amask) to an exhalation outlet 956 in the water bath 904 of the uprightcylinder 902, an annular region 958 between the outer container wall ofthe upright cylinder 902 and the inner container wall of the invertedcylinder 906. Disposed in the inhalation line 922 downstream of theinhalation valve 940 (between the inhalation valve 940 and the patient)is a manometer 970 containing a non-toxic electrolytic liquid 974. Theinner cylinder's free surface 912 will always be lower than the outercylinder's free surface 944 (the height difference corresponds to thehydrostatic delivery pressure).

The main difference between the ICHV apparatus 900 of FIG. 9 and theICHV apparatus 800 of FIG. 8 is that the inhalation line 922 and theexhalation line 952 do not merge into a single patient breathing linecoupled to the patient but remain separate and are separately coupled tothe patient. Furthermore, the ICHV apparatus 900 does not include abubbler bypass valve 830 provided on a bubbler bypass line 832 asprovided in the ICHV apparatus 800.

The operation of the ICHV apparatus 900 is substantially identical tothe operation of the ICHV apparatus 800. It is simpler because the ICHV900 does not have to operate the absent bubbler bypass valve 830 in thebubbler bypass line 832 of the ICHV apparatus 800. The opening andclosing of the inhalation valve 940 in the inhalation line 922 and theexhalation valve 950 in the exhalation line 952 are similar to theopening and closing of the inhalation valve 840 in the inhalation line822 and the exhalation valve 850 in the exhalation line 852. Because theinhalation line 922 and the exhalation line 952 do not merge into asingle patient breathing line (in which there is two-way air flow),there may be less restrictions or requirements on the operation of theinhalation valve 940 and the exhalation valve 950 and coordination ofthe operation in the separate inhalation line 922 and exhalation line952 (in which there is one-way air flow in each). This separation offlows also avoids “dead air” residing and oscillating in the tubingbetween the ICHV and patient. In a single tube design, the potentialexists for residual quantities of exhaled gas from a previous breath toremain in the tube only to be fed back to the patient in the initialstage of new breath delivery.

FIG. 10 shows an example of an evaporation and humidification inhibitorfor a PEEP tube 1010. If long-term use of the non-conditioning mode isintended, a thin layer of non-toxic oil with low volatility and specificgravity less than one, such as partially-hydrogenated vegetable oil orfood-grade mineral oil, may be employed as an evaporation andhumidification inhibitor 1020 over a water reservoir. The oil blanketcan be located on the water free surface (212 in FIG. 2A) within theinner cylinder (to minimize humidification), the water free surface of(244 in FIG. 2A) the outer cylinder (to minimize evaporation to theambient environment), or both free surfaces. The PEEP tube 1010terminates in its own separate sterilization reservoir with permeablemembrane shown near the top of the free surface or a hydraulicallyseparate PEEP reservoir to reduce PEEP variability during operation andto possibly aid in exhaled air sterilization.

FIG. 11 shows an example of a smaller reservoir 1140 of water 1150treated with a sterilizing agent (dissolved biocidal chemical or UV-Cirradiation, for example) located either outside or, space permitting,inside the outer cylinder 802, but hydraulically separated from the mainwater bath 804, for housing the reentrant PEEP tube terminus 856. Apermeable membrane, such as woven cotton, located below the surface ofthis PEEP bath 1150 may help break apart the large exhalation bubbles,mitigating sterilization further by increasing residency time and gassurface area. Another advantage to this arrangement is a more-consistentwater level reducing the PEEP value's operationally unintendedvariability during inner cylinder 806 movement; adjustability by theuser is still maintained. An evaporation and humidification inhibitor1160 (e.g., oil blanket) is located on the water free surface 812 withinthe inner cylinder (to minimize humidification) and the water freesurface 844 of the outer cylinder (to minimize evaporation to theambient environment). The ICHV apparatus 800B of FIG. 11 is a modifiedversion of the ICHV apparatus 800 of FIG. 8 with like referencecharacters for like parts.

The apparatus may be thought of as having means for directing abreathing gas to the inverted container space, to move the invertedcontainer upward from a preset minimum elevation position when thebreathing gas in the inverted container space reaches a hydrostaticdelivery pressure, to continue moving the inverted container upward atthe hydrostatic delivery pressure while a volume of the invertedcontainer space increases at the hydrostatic delivery pressure, to stopmoving the inverted container upward when the inverted container reachesa preset maximum elevation position, and to move the inverted containerupward at the hydrostatic delivery pressure when the inverted containerdrops from the preset maximum elevation position to the preset minimumelevation position. In one example, such means may include the gassupply line 220, air pump 221, bubbler bypass valve 230, and inhalationvalve 240. The means may further include the manometer 310 (having theelectrolytic liquid 314 and connected to the patient breathing line 260or the inhalation line 222) and the sensing wire 340, and/or may furtherinclude proximity sensor 500, reference voltage line 510, and uppersensing wire 520, and/or may further include the ultrasonic rangingsensor 610, and/or may further include the controller 130, 540, and/or620. In another example, the means may include the gas supply line 820,bubbler bypass valve 830, bubbler bypass line 832, and inhalation valve840. The means may further include the manometer 870 and/or may furtherinclude the proximity sensor 500, reference voltage line 510, uppersensing wire 520, and lower sensing wire 530, and/or may further includethe ultrasonic ranging sensor 610, and/or may further include thecontroller 130, 540, and/or 620. In another example, the means mayinclude the gas supply line 920, inhalation valve 940, and gas supplyvalve 980. The means may further include the manometer 970, and/or mayfurther include the proximity sensor 500, reference voltage line 510,upper sensing wire 520, and lower sensing wire 530, and/or may furtherinclude the ultrasonic ranging sensor 610, and/or may further includethe controller 130, 540, and/or 620.

The apparatus may also be thought of as having means for directing anexhalation gas flow, when the inverted container has reached the presetminimum elevation position, to permit the exhalation gas flow from thepatient through the exhalation inlet to the exhalation outlet disposedin the liquid between the inverted container wall and the outercontainer wall, and, based on one of (1) detection of the targethydrostatic backpressure at the exhalation outlet or (2) a second presettiming, to stop the exhalation gas flow from the exhalation inlet to theexhalation outlet in the liquid at the fixed elevation. In one example,such means may include the exhalation valve 250 or 850 or 950. The meansmay further include the proximity sensor 500, reference voltage line510, and lower sensing wire 530, and/or may further include theultrasonic ranging sensor 610, and/or may further include the controller130, 540, and/or 620.

ICHV Apparatus Characteristics

The ICHV apparatus may have different configurations with differentcharacteristics including available tidal volume, delivery pressure,operational mass, and various dimensions. The various components can becustom-made using a variety of materials and processes or commerciallyavailable, at different price ranges. The present invention can beimplemented based on various operational needs and budget constraints.

If less pressure and/or tidal volume is needed, it can be easilymodified to suit the providers' needs with regard to tidal volume anddelivery pressure or even modularized via optional extensions to make ittaller (taller=greater capacity for pressure and volume).

FIG. 12 shows a graph of available tidal volume, added mass, and maximumunit height versus delivery pressure of the baseline ICHV apparatus ofFIG. 8 . The added mass refers to the adjustable cylinder weights addedto the inverted cylinder 606, for example, by placing them on top of theclosed top 608 of the inverted cylinder 606. The dimensions ofbreadth-width-height (BWH) are as follows: BWH_(min) of 12.4 cm×12.4cm×57.9 cm (shipping dimension) and BWH_(max) of 12.4 cm×12.4 cm×104.4cm (when delivering max. tidal volume at min. pressure).

The operational mass is about 10 to 12 kg (water+cylinder weight=7.73 kgplus structure/valves/tubes). The operational water volume needed is2.66 L when delivering maximum pressure (min. tidal volume) and is 7.73L when delivering maximum tidal volume (min. delivery pressure).

The available tidal volume has an inverse relationship with the deliverypressure. The available PEEP range is 0 to 53 cmH₂O if the PEEP tubeterminates in the main reservoir. The available tidal volume range(example setpoints; pressure & volume are analog adjustments) is 0 to1,070 mL when delivered at 40 cmH₂O, is 0 to 3,070 mL when delivered at20 cmH₂O, is 0 to 3,570 mL when delivered at 15 cmH₂O, is 0 to 4,070 mLwhen delivered at 10 cmH₂O, and is 0 to 4,570 mL when delivered at 5cmH₂O.

Patient Ventilator Mask

In one example, the ventilator mask 120 of FIG. 1 is an existing maskmodified to replace filters with valves. The mask may be connected to aninhalation line having an inhalation valve and an exhalation line havingan exhalation valve. It can maintain a net positive pressure in theplenum between the mask and the patient's nose and mouth. It allowslow-pressure breathing air to enter the plenum as dictated either by acontroller (e.g., mandatory breathing operation) or by cues from thepatient (e.g., on-demand breathing operation). It allows air to beexhaled through a separate valve, either by the predetermined controlschedule (e.g., mandatory breathing) or by cues from the patient (e.g.,on-demand breathing). It allows the patient to inhale and exhale freelyin the event of a control failure or external valve system failure.

In one embodiment, a commercially available mask is modified to have theabove features. The mask has attached filters. In its respirator mode,the user inhales air through the filters and exhales air through acentral valve. Alternate or new filters can be purchased andreinstalled.

In the modified ventilator mask, one of the inlet non-return valves isdefeated by removing the flapper valve from inside the mask. This nowbecomes the exhale port and is opened and closed by a downstreamsolenoid valve and then vented, through an appropriate filter to theatmosphere. The original exhale valve is reversed by taking flappervalve from outside of the mask and re-fitting inside the mask. Thisvalve now acts as an emergency inhale port in case of failure of theremaining inlet valve (e.g., a solenoid upstream of the respirator staysclosed due to some failure). In normal operation, the positive pressuremaintained in the plenum between the mask and the user's face keeps thisemergency valve closed. The remaining inhale valve is left untouched.The two original filters of the respirator are removed and replaced bytwo ventilator valve adaptors.

To allow air tubes to be connected to the mask, an adapter connection ismade using the pair of ventilator valve adaptors having proximalportions attached to the two original inhale ports. The ventilator valveadaptors have distal portions to be attached, via an inhalation port toan inhalation line having an inhalation valve and via an exhalation portto an exhalation gas line having an exhalation valve.

The manufacturing of the mask may involve printing PETG and moreflexible materials, as well as PETG, PET, PLA, and ABS. Themanufacturing process uses Ecoflex 0035 for the silicone mold and Task 8resin for the mask. Another process uses Wiles April 12 version withCheetah TPU. Yet another process is used to make a bunch of PLAs at 0.15mm layer height, about 10 ABS, 6 or so PETG at 30% and about as many at40, a few ABS at 30% infill and about as many 40%.

Controller

FIG. 13 illustrates an example of a controller or computing system 1300including logic. The computing system 1300 includes a processing system1310 having a hardware processor 1325 configured to perform a predefinedset of basic operations 1330 by loading corresponding ones of apredefined native instruction set of codes 1335 as stored in the memory1315. The computing system 1300 further includes input/output 1320having user interface 1350, display unit 1355, communication unit 1360,and storage 1365.

The memory 1315 is accessible to the processing system 1310 via the bus1370. The memory 1315 includes the predefined native instruction set ofcodes 1335, which constitute a set of instructions 1340 selectable forexecution by the hardware processor 1325. In an embodiment, the set ofinstructions 1340 include logic 1345 to perform the functions of theICHV apparatus as described above, including those summarized in theflow diagrams of FIG. 4 .

The various logic 1345 is stored in the memory 1315 and comprisesinstructions 1340 selected from the predefined native instruction set ofcodes 1335 of the hardware processor 1325, adapted to operate with theprocessing system 1310 to implement the process or processes of thecorresponding logic 1345.

In specific embodiments, the controller includes an Arduino controllerand breadboard, several resistors and LEDs, a voltage regulator, and apotentiometer. These control system components are assembled and placedin a housing.

FIGS. 14A-14G show an example of controller logic for operating an ICHVsystem according to an embodiment of the invention. It is noted thatthis example of the controller logic does not include the breath timingfunction. An additional feature that can be added is to provide a usersetting specifying the mandatory breath frequency in terms ofbreaths-per-minute.

The inventive concepts taught by way of the examples discussed above areamenable to modification, rearrangement, and embodiment in several ways.For example, the embodiments shown employ an inverted inner cylindricalcontainer and an upright outer cylindrical container, each having auniform cross-section. In other embodiments, the inverted innercontainer or the upright outer container or both may be non-cylindricalwith nonuniform cross-sections and/or nonuniform cross-sectional areasalong the height direction, or may be non-cylindrical with a uniformcross-sectional area. The calculations of volumes, pressures, andheights will be different as a result, but the apparatus operates on thesame principles.

Some embodiments of the ICHV system present low-tech, easy-to-fabricatearrangements to provide breathing gas to a patient's mask. The requiredinputs include: 1) compressed breathing gas supply, 2) electricity formicrocontroller, UV light, and heating element, and 3) distilled water.If only ambient air is available (i.e., no compressed breathing gassupply is available to supply breathing gas into a gas volume of theinverted cylinder space), a linear drive unit can be used to lift theinverted cylinder and a one-way valve is provided to allow atmosphericair to enter into the gas volume of the inverted cylinder space.

Variable Hydrostatic Pressure Embodiments

FIGS. 15, 17-19, and 21 show embodiments of variable hydrostaticpressure ventilator apparatus having a first container and a secondcontainer containing a liquid and being in fluidic communication witheach other via the liquid. The first container has a first liquidsurface at a first liquid surface elevation of the liquid. The secondcontainer has a second liquid surface at a second liquid surfaceelevation of the liquid. The second container includes a secondcontainer space surrounded by the second container and the second liquidsurface. A hydrostatic pressure in the second container space resultsfrom a pressure differential defined by a difference between the firstliquid surface elevation and the second liquid surface elevation.

FIG. 15 schematically illustrates the operation of a variablehydrostatic pressure ventilator (VHPV) apparatus 1500 with states(A)-(E) according to an embodiment employing a stationary inverted innercontainer 1506 (second container) disposed in an upright outer container1502 (first container) of a liquid.

Initially the liquid (e.g., water) level 1512 inside and liquid level1544 outside of the inverted inner container 1506 are the same (stateA). Breathing gas is introduced into the inverted inner container spaceor inverted chamber 1510 (second container space) of the inverted innercontainer 1506 via a gas supply line 1520, which displaces the liquiddownward and out its open bottom. For simplicity, the gas supply line1520 is also used as an inhalation line for supplying the breathing gasfrom the inverted inner container space 1510 to the patient via aninhalation outlet. In another example, the VHPV apparatus 1500 mayinclude similar gas supply line 820 and inhalation line 822 as shown inFIG. 8 .

The liquid level 1544 rises in the outside container 1502 and builds upand exerts the hydrostatic pressure in the inverted inner containerspace 1510, as defined by a height difference 1572 between the liquidlevel 1512 in the inverted inner container 1506 and the liquid level1544 in the outer container 1502 (state B). A maximum hydrostaticpressure is reached when the inverted inner container space 1510 expandsup to a maximum allowable size of the inverted inner container 1506 at aheight difference 1574 (state C). When a breath is administered from theinverted inner container space 1510 via an inhalation line 1520, theliquid flows back into the inverted inner container 1506 until thebreathing stops or a prescribed volume of breathing gas has beendelivered (at a height difference 1576 in state D or at a heightdifference 1578 in state E or at zero height difference in state Adepending on the amount of breathing gas delivered). An inhalationsensor may be coupled with the inhalation line to detect the patientbreath demand signal. The maximum hydrostatic pressure is adjustable andlimited by the size of the inverted inner container 1506 (state C); asis the delivered volume of breathing gas (e.g., state D or state E) andthe final pressure. Mathematically, the final pressure can reach as lowas the lowest safe threshold (e.g., state A as seen). Realistically, thefinal pressure may be configured to be higher to maintain positiveend-expiratory pressure (PEEP) against which the patient must exhale inorder to avoid collapse of the alveoli in the lungs. For instance, thefinal pressure at a level between state D and state E instead of level Amay be provided to keep the alveoli inflated. Examples of providing PEEPusing a variable-depth exhalation outlet (256, 856, 956) have been shownand described above in connection with FIGS. 2A-2H, 8, 9, and 11 . Theinverted inner container 1506 remains stationary throughout the staging(states A-E).

As mentioned above, in this simplified version, the inhalation line isthe same as the gas delivery line 1520. In another example, the VHPVapparatus 1500 may include similar gas supply line 820 and inhalationline 822 as shown in FIG. 8 . The inhalation line is configured to closeand the gas supply line is configured to supply the breathing gas to thesecond container space 1510 when the hydrostatic pressure in the secondcontainer space 1510 drops to a base hydrostatic pressure (e.g., back tostate A or to a higher level such as one between level D and level E tomaintain PEEP to keep the alveoli inflated). An exhalation line (e.g.,852 in FIG. 8 ) has an exhalation inlet to receive exhaled gas from thepatient and an exhalation outlet disposed in the liquid in the first orouter container 1502 and outside the second or inverted inner container1506. In an embodiment, when the hydrostatic pressure in the secondcontainer space 1510 has dropped to the base hydrostatic pressure, theexhalation line is opened to permit an exhalation gas flow from thepatient through the exhalation inlet to the exhalation outlet disposedin the liquid in the first container 1502 and outside the secondcontainer 1506, and the gas supply line 1520 supplies the breathing gasto flow to the second container space 1510.

The apparatus may be thought of as having means for expanding the secondcontainer space 1510 by directing a breathing gas from the gas supplyline 1520 to the second container space 1510 and contracting the secondcontainer space 1510 by permitting a flow of the breathing gas from theinhalation inlet in the second container space 1510 through theinhalation line to the inhalation outlet coupled to the patient.

FIG. 16 is a plot of the hydrostatic pressure over time of the VHPVapparatus of FIG. 15 . The pressure profile has a “delayed” sawtoothpattern. The shape of the pressure profile is an approximation of thestaging (states A-E) illustrated in FIG. 15 . The hydrostatic pressurein the second container space 1510 is variable from an inhalation starttime (state C) when the breathing gas flows from the inhalation inlet inthe second container space 1521 via the inhalation line to theinhalation outlet coupled to the patient, to an inhalation end time whenthe breathing gas stops flowing from the inhalation inlet in the secondcontainer space 1510 to the inhalation outlet (e.g., back to state A orto a higher level such as one between level D and level E as theoperational baseline pressure to maintain PEEP to keep the alveoliinflated). The plot does not account for PEEP at the completion of eachbreath. Patients requiring PEEP will experience a similar sawtoothpattern with a slightly elevated minimum pressure higher than thatindicated by state A.

FIG. 17 schematically illustrates the operation of a VHPV apparatus 1700with states (A)-(E) according to another embodiment employing astationary inverted inner container 1706 (second container) disposed inan upright outer container 1702 (first container) of a liquid. The maindifference between the VHPV apparatus 1700 of FIG. 17 and that of FIG.15 is that the inverted inner container 1706 in the VHPV apparatus 1700of FIG. 17 has a shorter height and/or smaller volume.

Initially the liquid level 1712 inside and liquid level 1744 outside ofthe inverted inner container 1706 are the same (state A). Breathing gasis introduced into the inverted inner container space 1710 (secondcontainer space) of the inverted inner container 1706 via a gas supplyline 1720, which displaces the liquid downward and out its open bottom.For simplicity, the gas supply line 1720 is also used as an inhalationline for supplying the breathing gas from the inverted inner containerspace 1710 to the patient. In another example, the VHPV apparatus 1700may include similar gas supply line 820 and inhalation line 822 as shownin FIG. 8 .

The liquid level 1744 rises in the outside container 1702 and builds upand exerts the hydrostatic pressure in the inverted inner containerspace 1710, as defined by a height difference 1772 between the liquidlevel 1712 in the inverted inner container 1706 and the liquid level1744 in the outer container 1702 (state B). A maximum hydrostaticpressure is reached when the inverted inner container space 1710 expandsup to a maximum allowable size of the inverted inner container 1706 at aheight difference 1774 (state C). When a breath is administered from theinverted inner container space 1710, the liquid flows back into theinverted inner container 1706 via an inhalation line 1720 until thebreathing stops or a prescribed volume of breathing gas has beendelivered (at a height difference 1776 in state D or at a heightdifference 1778 in state E or at zero height difference in state Adepending on the amount of breathing gas delivered). An inhalationsensor may be coupled with the inhalation line to detect the patientbreath demand signal. The maximum hydrostatic pressure is adjustable andlimited by the size of the inverted inner container 1606 (state C); asis the delivered volume of breathing gas (e.g., state D or state E) andthe final pressure. The inverted inner container 1706 remains stationarythroughout the staging (states A-E).

The inhalation line is configured to close and the gas supply line isconfigured to supply the breathing gas to the second container space1710 when the hydrostatic pressure in the second container space 1710drops to a base hydrostatic pressure (e.g., back to state A or to ahigher level such as one between level D and level E as the operationalbaseline pressure to maintain PEEP to keep the alveoli inflated). Anexhalation line (e.g., 852 in FIG. 8 ) has an exhalation inlet toreceive exhaled gas from the patient and an exhalation outlet disposedin the liquid in the first or outer container 1702 and outside thesecond or inverted inner container 1706. In an embodiment, when thehydrostatic pressure in the second container space 1710 has dropped tothe base hydrostatic pressure, the exhalation line is opened to permitan exhalation gas flow from the patient through the exhalation inlet tothe exhalation outlet disposed in the liquid in the first container 1702and outside the second container 1706, and the gas supply line 1720supplies the breathing gas to flow to the second container space 1710.

The hydrostatic pressure profile for the VHPV apparatus 1700 of FIG. 17is similar in shape to the pressure profile shown in FIG. 16 for theVHPV apparatus 1500 of FIG. 15 . It also has a “delayed” sawtoothpattern and the shape is merely an approximation of the staging (statesA-E) illustrated in FIG. 17 .

FIG. 18 schematically illustrates the operation of a VHPV apparatus 1800with states (A)-(E) according to an embodiment employing two separatecontainers connected via a fluid conduit through which a liquid flowstherebetween. FIG. 18 shows a first container or chamber 1802 disposedentirely at a higher elevation than a second container or chamber 1806and connected to the first container 1802 via a fluid conduit or pipe1803. In that embodiment, in the default state (A), the liquid isdisposed completely in the second (lower) container 1806. Breathing gasis introduced into a (second) lower container space 1810 of the lowercontainer 1806 via a gas supply line 1820, which displaces the liquidupward and pushes it out via the fluid conduit 1803 into a (first) uppercontainer space 1807 of the upper container 1802. For simplicity, thegas supply line 1820 is also used as an inhalation line for supplyingthe breathing gas from the inverted inner container space 1810 to thepatient. In another example, the VHPV apparatus 1800 may includeseparate gas supply line and inhalation line.

The liquid level 1812 drops in the lower container 1806 and builds upand exerts the hydrostatic pressure in the lower container space 1810 asthe liquid level 1844 in the upper container 1802 rises (state B). Thetwo containers are hydraulically linked. The height difference 1872between the liquid surface level 1844 in the first or upper container1802 and the liquid surface level 1812 in the second or lower container1806 determines the hydrostatic pressure in the lower container space1810 as the hydrostatic delivery pressure of the breathing gas flowingfrom the lower container space 1810 to the patient. A maximumhydrostatic pressure is reached at the maximum height difference whenthe liquid level 1812 in the lower container 1806 drops to a minimumlevel and/or the liquid level 1844 in the upper container 1802 rises toa maximum level at a height difference 1874 (state C). In the exampleshown, the minimum level is at the minimum allowable level of zeroheight as all the liquid remains in the lower container 1806 (state A)and the maximum level is the maximum allowable level of maximum heightas the liquid exits the lower container 1806 and fills the entire uppercontainer 1802 (state C). In other examples, the minimum level in thelower container 1806 may be at some height above zero and the maximumlevel in the upper container 1802 may be at some height below themaximum height.

When a breath is administered from the (second) lower container space1810, the liquid flows back into the lower container 1806 from the uppercontainer 1802 until the breathing stops or a prescribed volume ofbreathing gas has been delivered (at a height difference 1876 in state Dor at a height difference 1878 in state E or at zero height differencestate A depending on the amount of breathing gas delivered). The maximumhydrostatic pressure is adjustable and limited by the size of the lowercontainer 1806 (state C); as is the delivered volume of breathing gas(e.g., state D or state E) and the final pressure. The peak hydrostaticdelivery pressure is determined and set by adjusting the elevation ofthe liquid surface 1844 of the upper container 1802 relative to theelevation of the liquid surface 1812 of the lower container 1806 (i.e.,adjusting the height differential 1874 in state C). Wider and flattercontainers will result in less pressure variation versus relative liquidelevations or heights. The inhalation line is configured to close andthe gas supply line is configured to supply the breathing gas to thesecond container space 1810 when the hydrostatic pressure in the secondcontainer space 1810 drops to a base hydrostatic pressure (e.g., back tostate A or to a higher level such as one between level D and level E asthe operational baseline pressure to maintain PEEP to keep the alveoliinflated). An exhalation line has an exhalation inlet to receive exhaledgas from the patient and an exhalation outlet disposed in the liquid inthe first or upper container 1802 and outside the second or lowercontainer 1806. In an embodiment, when the hydrostatic pressure in thesecond container space 1810 has dropped to the base hydrostaticpressure, the exhalation line is opened to permit an exhalation gas flowfrom the patient through the exhalation inlet to the exhalation outletdisposed in the liquid in the first container 1802 and outside thesecond container 1806, and the gas supply line 1820 supplies thebreathing gas to flow to the second container space 1810.

In alternate embodiments, the first container 1802 may be disposedpartially instead of completely above the second container 1806 or mayeven be disposed at the same elevation as the second container 1806 in aside-by-side configuration. The first container 1802 and the secondcontainer 1806 may be spaced apart from one another with no overlap. Insome examples, the first container 1802 may have a greater height and/orsize than the second container 1806 to receive the liquid from thesecond container 1806. In other examples, the liquid may not completelyfill either container and may not completely empty out of eithercontainer in the manner shown in state (A) or state (C) of FIG. 18 .

The hydrostatic pressure profile for the VHPV apparatus 1800 of FIG. 18is similar in shape to the pressure profile shown in FIG. 16 for theVHPV apparatus 1500 of FIG. 15 . It also has a “delayed” sawtoothpattern and the shape is merely an approximation of the staging (statesA-E) illustrated in FIG. 18 .

FIG. 19 schematically illustrates the operation of a VHPV apparatus 1900with states (A)-(F) according to an embodiment employing a movableinverted inner container 1906 (second container) disposed in an uprightouter container 1902 (first container) of a liquid and being biased by aspring 1905 in a direction opposing lowering of the elevation of theinverted inner container 1906. The movable container 1906 floatsrelative to the liquid in the outer container 1902 and is coupled to theouter container 1902 via the spring 1905. The spring 1905 is compressedto exert an upward force which is not strong enough to overcome theweight of the inverted inner container 1906 (low value of springconstant) to lift it (state A).

Initially the liquid level 1912 inside and liquid level 1944 outside ofthe inverted inner container 1906 are the same (state A). Breathing gasis introduced into the inverted inner container space 1910 (secondcontainer space) of the inverted inner container 1906 via a gas supplyline 1920, which displaces the liquid downward and out its open bottom.The liquid level 1944 rises in the outside container 1902 and builds upand exerts the hydrostatic buoyancy-inducing pressure in the invertedinner container space 1910, as defined by a height difference 1970between the liquid level 1912 in the inverted inner container 1906 andthe liquid level 1944 in the outer container 1902 (state B). Thehydrostatic pressure is determined or defined by the height difference1970 between the liquid surface 1912 in the inverted inner container1906 and the liquid surface 1944 in the outer container 1902. Whenenough gas has been introduced into the inverted inner container space1910 and the hydrostatic pressure reaches a certain level sufficient, incombination with the spring force, to overcome the weight of theinverted inner container 1906, the inverted inner container space 1910becomes positively buoyant. The inverted inner container 1906 movesupward as the inverted inner container space 1910 expands to a heightdifference 1972 (state C). A maximum hydrostatic pressure is reachedwhen the inverted inner container space 1910 expands up to a maximumallowable size of the inverted inner container 1906 (state D). Themaximum height difference 1974 which the liquid level 1912 in theinverted inner container 1906 achieves relative to the liquid level 1944in the outer container 1902 is limited by the lower lip or open bottom1911 of the inverted inner container coinciding with the lowest extentof the gas in the inverted inner container space, resulting in a maximumheight difference of 1974 between the liquid surface 1912 in theinverted inner container 1906 and the liquid surface 1944 in the outercontainer 1902.

When a breath is administered from the inverted inner container space1910 via an inhalation line (not shown for simplicity; an example issimilar to the inhalation line 824 in FIG. 8 ), the liquid flows backinto the inverted inner container 1906 and it drops or is lowered inelevation until the breathing stops or a prescribed volume of breathinggas has been delivered (at a height difference 1976 in state E or at aheight difference 1978 in state F or at zero height difference in stateA depending on the amount of breathing gas delivered). The spring 1905provides linearly increasing resistance to further lowering of theelevation of the inverted inner container 1906. An inhalation sensor maybe coupled with the inhalation line to detect the patient breath demandsignal. The maximum hydrostatic pressure is adjustable and limited bythe size of the inverted inner container 1906 (state D); as is thedelivered volume of breathing gas (e.g., state E or state F) and thefinal pressure.

The inhalation line is configured to close and the gas supply line 1920is configured to supply the breathing gas to the second container space1910 when the hydrostatic pressure in the second container space 1910drops to a base hydrostatic pressure (e.g., back to state A or to ahigher level such as one between level A and level F as the operationalbaseline pressure to maintain PEEP to keep the alveoli inflated). Anexhalation line (e.g., 852 in FIG. 8 ) has an exhalation inlet toreceive exhaled gas from the patient and an exhalation outlet disposedin the liquid in the first or outer container 1902 and outside thesecond or inverted inner container 1906. In an embodiment, when thehydrostatic pressure in the second container space 1910 has dropped tothe base hydrostatic pressure, the exhalation line is opened to permitan exhalation gas flow from the patient through the exhalation inlet viathe exhalation line to the exhalation outlet disposed in the liquid inthe first container 1902 and outside the second container 1906, and thegas supply line 1920 supplies the breathing gas to flow to the secondcontainer space 1910.

FIG. 20 is a plot of the hydrostatic pressure over time of the VHPVapparatus 1900 of FIG. 19 . The pressure profile has a “delayed” 2-slopesawtooth pattern. The shape of the pressure profile is an approximationof the staging (states A-F) illustrated in FIG. 19 . The first stage(state D to state E to state F) represents lowering of the invertedinner container 1906 as the hydrostatic pressure drops and the invertedinner container space 1910 contracts. The second stage (state F to stateA) represents contraction of the inverted inner container space 1910 andcorresponding drop in the hydrostatic pressure while the inverted innercontainer 1906 remains stationary at its minimum elevation. Thehydrostatic pressure in the second container space 1910 is variable froman inhalation start time (state D) when the breathing gas flows from theinhalation inlet in the second container space 1921 via the inhalationline to the inhalation outlet coupled to the patient, to an inhalationend time when the breathing gas stops flowing from the inhalation inletin the second container space 1910 to the inhalation outlet (e.g., backto state A or to a higher level such as one between level A and level Fas the operational baseline pressure to maintain PEEP to keep thealveoli inflated). The plot does not account for PEEP at the completionof each breath. Patients requiring PEEP will experience a similarmodified sawtooth pattern with a slightly elevated minimum pressurehigher than that indicated by state A.

FIG. 21 schematically illustrates the operation of a VHPV apparatus 2100with states (A)-(G) according to an embodiment employing a movableinverted inner container 2106 (second container) disposed in an uprightouter container 2102 (first container) of a liquid and being biased by aspring 2105 in a direction opposing lowering of the elevation of theinverted inner container 2106 until the inverted inner container 2106rises above a level free of the spring loading. The spring 2105 incompression biases the inverted container 2106 in a direction opposinglowering of the elevation of the inverted container 2106 until theinverted container 2106 rises above the spring 2105 after the spring2105 is free from compression and is free from biasing by the spring2105. The movable container 2106 floats relative to the liquid in theouter container 2102 and is coupled to the outer container 2102 via thespring 2105. The spring 2105 is compressed to exert an upward forcewhich is not strong enough to overcome the weight of the inverted innercontainer 2106 (low value of spring constant) to lift it (state A).

Initially the liquid level 2112 inside and liquid level 2144 outside ofthe inverted inner container 2106 are the same (state A). Breathing gasis introduced into the inverted inner container space 2110 (secondcontainer space) of the inverted inner container 2106 via a gas supplyline 2120, which displaces the liquid downward and out its open bottom.The liquid level 2144 rises in the outside container 2102 and builds upand exerts the hydrostatic buoyancy-inducing pressure in the invertedinner container space 2110, as defined by a height difference 2170between the liquid level 2112 in the inverted inner container 2106 andthe liquid level 2144 in the outer container 2102 (state B). Thehydrostatic pressure is determined or defined by the height difference2170 between the liquid surface 2112 in the inverted inner container2106 and the liquid surface 2144 in the outer container 2102. Whenenough gas has been introduced into the inverted inner container space2110 and the hydrostatic pressure reaches a certain level sufficient, incombination with the spring force, to overcome the weight of theinverted inner container 2106, the inverted inner container space 2110becomes positively buoyant. The inverted inner container 2106 movesupward as the inverted inner container space 2110 expands to a heightdifference 2172 (state C). States A to C in FIG. 21 are similar tostates A to C in FIG. 19 .

In state D, the inverted inner container 2106 rises to an elevation to aheight difference 2174 at which the spring 2105 is no longer compressed.Contact between the inverted inner container 2106 and the spring 2105may be lost, at which point only buoyancy from the induced gas flow intothe inverted inner container space 2110 causes the inverted innercontainer 2106 to rise without spring assistance. The inverted innercontainer space 2110 continues to expand while the height difference2174 remains the same from state D to state E. The inverted container2110 is configured to move upward from a first elevation position whenthe breathing gas in the second container space 2110 reaches a thresholdhydrostatic pressure (state D) and to continue moving upward while thevolume of the inverted container space 2110 increases, The invertedcontainer 2106 is configured to stop moving upward and the gas supplyline 2120 is configured to stop supplying the breathing gas to theinverted container space 2110 when the inverted container 2106 reaches asecond elevation position (e.g., preset maximum as limited by the lowerlip or open bottom of the inverted inner container 2110 coinciding withthe lowest extent of the gas in the inverted inner container space2110). A maximum hydrostatic pressure is reached when the inverted innercontainer space 2110 expands up to a maximum allowable size of theinverted inner container 2106. The liquid level 2112 in the invertedinner container 2106 reaches the maximum height difference 2174 relativeto the liquid level 2144 in the outer container 2102 when the invertedinner container 2106 rises to an elevation above the free spring 2105(state D). The height difference 2174 remains the same as long as theelevation of the inverted inner container 2106 stays above the freespring 2105 (state D and state E), regardless of the actual elevation ofthe inverted inner container 2106.

When a breath is administered from the inverted inner container space2110, the liquid flows back into the inverted inner container 2106 andit drops or is lowered in elevation until the breathing stops or aprescribed volume of breathing gas has been delivered (at a heightdifference 2176 in state F or at a height difference 2178 in state G orat zero height difference in state A depending on the amount ofbreathing gas delivered). The spring 2105 provides linearly increasingresistance to further lowering of the elevation of the inverted innercontainer 2106. The maximum hydrostatic pressure is adjustable andlimited by the position of the inverted inner container 2106 relative tothe free spring 2105 (state D and state E); as is the delivered volumeof breathing gas (e.g., state F or state G) and the final pressure.

The inhalation line is configured to close and the gas supply line 2120is configured to supply the breathing gas to the second container space2110 when the hydrostatic pressure in the second container space 2110drops to a base hydrostatic pressure (e.g., back to state A or to ahigher level such as one near level G or between level A and level G asthe operational baseline pressure to maintain PEEP to keep the alveoliinflated). An exhalation line (e.g., 852 in FIG. 8 ) has an exhalationinlet to receive exhaled gas from the patient and an exhalation outletdisposed in the liquid in the first or outer container 2102 and outsidethe second or inverted inner container 2106. In an embodiment, when thehydrostatic pressure in the second container space 2110 has dropped tothe base hydrostatic pressure, the exhalation line is opened to permitan exhalation gas flow from the patient through the exhalation inlet tothe exhalation outlet disposed in the liquid in the first container 2102and outside the second container 2106, and the gas supply line 2120supplies the breathing gas to flow to the second container space 2110.

FIG. 22 is a plot of the hydrostatic pressure over time of the VHPVapparatus 2200 of FIG. 21 . The pressure profile has a “delayed” 3-slopesawtooth pattern. The shape of the pressure profile is an approximationof the staging (states A-G) illustrated in FIG. 21 . The first stage(state D to state E) is an initial constant pressure stage whichrepresents free rising and lowering of the inverted inner container 2106relative to the free spring 2105 at a constant height difference 2174 asthe inverted inner container space 2110 expands and contracts withoutspring resistance. The second state represents contraction of theinverted inner container space 2110 while the inverted inner container2106 drops in elevation and compresses the spring 2105 to state F at aheight difference 2176 with spring compression and to state G at aheight difference 2178. The third stage (state G to state A) representsfurther contraction of the inverted inner container space 2110 andcorresponding drop in the hydrostatic pressure while the inverted innercontainer 2106 remains stationary at its minimum elevation. The pressuredrop in third stage is due to the liquid free surfaces 2112 & 2144equalizing between the inverted inner container 2106 and the outercontainer 2102 after the spring 2105 has been fully compressed. Thehydrostatic pressure in the second container space 2110 is variable froman inhalation start time (state E) when the breathing gas flows from theinhalation inlet in the second container space 2121 to the inhalationoutlet coupled to the patient, to an inhalation end time when thebreathing gas stops flowing from the inhalation inlet in the secondcontainer space 2110 to the inhalation outlet (e.g., back to state A orto a higher level such as one near level G or between level A and levelG as the operational baseline pressure to maintain PEEP to keep thealveoli inflated). The plot does not account for PEEP at the completionof each breath. Patients requiring PEEP will experience a similarmodified sawtooth pattern with a slightly elevated minimum pressurehigher than that indicated by state A.

FIG. 23 is a schematic illustration of another embodiment of the VHPVaccording to an embodiment employing multiple inverted inner containersdisposed in an outer container 2302 of a liquid. The VHPV apparatus 2300is similar to the ICHV apparatus 800 of FIG. 8 but includes multipleinverted inner containers 2306A-2306D having closed tops and invertedcontainer spaces 2310A-2310D trapped by a water bath 2304 withcorresponding distributed inhalation lines or tubes 2322A-2322D withinhalation inlets 2324A-2324D. The distributed inhalation lines2322A-2322D have corresponding distributed inhalation line valves(one-way) 2323A-2323D upstream of an inhalation valve 2340.

The VHPV apparatus 2300 includes the following similar components: anupright outer cylinder 2302 containing a water bath 2304, gas volumes inthe inverted container spaces 2310A-2310D trapped by the water bath 2304in the upright container 2302 above inverted inner container free watersurfaces 2312A-2312D, a gas supply line or tube 2320, a bubbler bypassvalve (one-way) 2330 provided on a bubbler bypass line or tube 2332, abubbler 2334, the inhalation or inspiratory valve or patient gasdelivery valve (one-way) 2340 provided on a patient supply (or patientgas delivery) or inhalation line or tube 2322 to supply breathing gas tothe distributed inhalation lines 2322A-2322D, an exhalation orexpiratory valve (one-way) 2350 provided on an exhalation line or tube2352 to permit exhaled breath of the patient to flow, in an openedposition, from an exhalation inlet coupled to the patient (e.g., via amask) to an exhalation outlet 2356 in the water bath 2304 of the uprightcontainer 2302, an annular region 2358 between the upright cylinder 2302and the inverted containers 2306A-2306D. The distributed inhalationlines 2322A-2322D are connected to the inhalation line 2322. Theinhalation line 2322 and the exhalation line 2352 merge at a junction2362 into a single patient breathing line 2360 coupled to the patient.Disposed between the junction 2362 and the exhalation valve 2350 is amanometer 2370 containing a non-toxic electrolytic liquid 2374. Thesingle patient breathing line 2360 leads to a breathing line opening2366 coupled to the patient, which is the inhalation outlet duringinhalation by the patient and the exhalation inlet during exhalation bythe patient. The inner containers' free surfaces 2312A-2312D will alwaysbe lower than the outer cylinder's free surface 2344 (the heightdifference corresponds to the hydrostatic delivery pressure).

The plurality of second containers 2306A-2306D are in fluidiccommunication with the first container 2302 via the liquid and each havea respective second liquid surface 2312A-2312D at a respective secondliquid surface elevation of the liquid. Each second container2306A-2306D includes a respective second container space 2310A-2310Dsurrounded by the respective second container 2306A-2306D and therespective second liquid surface 2312A-2312D. A respective hydrostaticpressure in the respective second container space 2310A-2310D resultsfrom a pressure differential defined by a difference between the firstliquid surface (2312A-2312D) elevation and the second liquid surface(2344) elevation. The gas supply line 2320 is configured to supply thebreathing gas to respective second container spaces 2310A-2310D of theplurality of second containers 2306A-2306D. The distributed inhalationlines 2322A-2322D have respective inhalation inlets 2324A-2324D in therespective second container spaces 2310A-2310D and an inhalation outletoutside of the liquid and outside of the plurality of second containers2306A-2306D to provide the breathing gas from the respective secondcontainer spaces 2310A-2310D to the patient. The respective secondcontainer spaces 2310A-2310D increase in size with an increase in thebreathing gas supplied from the gas supply line 2320 to the respectivesecond container spaces 2310A-2310D. The respective inhalation line2322A-2322D is configured to open to permit the flow of the breathinggas from the respective inhalation inlets 2324A-2324D in the respectivesecond container spaces 2310A-2310D to the inhalation outlet coupled tothe patient, causing the respective second container spaces 2310A-2310Dto decrease in size. A gas supply valve 2380 is used to control supplyof the breathing gas from the gas supply line 2320 to the respectivesecond container spaces 2310A-2310D after positioning the gas supplyline outlet (with or without the bubbler 2334) in the respective secondcontainers 2306A-2306D. The distributed inhalation line valves2323A-2323D are used to control the flow of the breathing gas from therespective inhalation inlets 2324A-2324D in the respective secondcontainer spaces 2310A-2310D to the inhalation outlet coupled to thepatient.

The distributed inhalation lines 2322A-2322D with correspondingdistributed inhalation line valves 2323A-2323D allow breathing gas to bewithdrawn, selectively, from the corresponding inverted container spaces2310A-2310D by controlling the opening and closing of the distributedinhalation line valves 2323A-2323D. The hydrostatic pressure fordelivering the breathing gas to the patient can vary and change bycontrolling the valves 2322A-2322D. The valves 2322A-2322D may be openedone at a time with the other valves closed, although it is possible toopen multiple valves 2322A-2322D at a time to allow the breathing gas toflow to the patient from multiple inverted container spaces 2310A-2310Dat any given time. As such, the hydrostatic delivery pressure fordelivering the breathing gas to the patient is variable

Accordingly, although the present disclosure has been described withreference to specific embodiments and examples, persons skilled in theart will recognize that changes may be made in form and detail withoutdeparting from the spirit and scope of the disclosure.

Certain attributes, functions, steps of methods, or sub-steps of methodsdescribed herein may be associated with physical structures orcomponents, such as a module of a physical device that, inimplementations in accordance with this disclosure, make use ofinstructions (e.g., computer executable instructions) that are embodiedin hardware, such as an application specific integrated circuit,computer-readable instructions that cause a computer (e.g., ageneral-purpose computer) executing the instructions to have definedcharacteristics, a combination of hardware and software such asprocessor implementing firmware, software, and so forth so as tofunction as a special purpose computer with the ascribedcharacteristics. For example, in embodiments a module may comprise afunctional hardware unit (such as a self-contained hardware or softwareor a combination thereof) designed to interface the other components ofa system such as through use of an API. In embodiments, a module isstructured to perform a function or set of functions, such as inaccordance with a described algorithm. This disclosure may usenomenclature that associates a component or module with a function,purpose, step, or sub-step to identify the corresponding structurewhich, in instances, includes hardware and/or software that function fora specific purpose. For any computer-implemented embodiment, “means plusfunction” elements will use the term “means;” the terms “logic” and“module” and the like have the meaning ascribed to them above, if any,and are not to be construed as means.

The claims define the invention and form part of the specification.Limitations from the written description are not to be read into theclaims.

An interpretation under 35 U.S.C. § 112(f) is desired only where thisdescription and/or the claims use specific terminology historicallyrecognized to invoke the benefit of interpretation, such as “means,” andthe structure corresponding to a recited function, to include theequivalents thereof, as permitted to the fullest extent of the law andthis written description, may include the disclosure, the accompanyingclaims, and the drawings, as they would be understood by one of skill inthe art.

To the extent the subject matter has been described in language specificto structural features and/or methodological steps, it is to beunderstood that the subject matter defined in the appended claims is notnecessarily limited to the specific features or steps described. Rather,the specific features and steps are disclosed as example forms ofimplementing the claimed subject matter. To the extent headings areused, they are provided for the convenience of the reader and are not betaken as limiting or restricting the systems, techniques, approaches,methods, devices to those appearing in any section. Rather, theteachings and disclosures herein can be combined, rearranged, with otherportions of this disclosure and the knowledge of one of ordinary skillin the art. It is the intention of this disclosure to encompass andinclude such variation. The indication of any elements or steps as“optional” does not indicate that all other or any other elements orsteps are mandatory.

What is claimed is:
 1. A ventilator comprising: a first container and asecond container containing a liquid and being in fluidic communicationwith each other via the liquid, the first container having a firstliquid surface at a first liquid surface elevation of the liquid, thesecond container having a second liquid surface at a second liquidsurface elevation of the liquid, the second container including a secondcontainer space surrounded by the second container and the second liquidsurface, and a hydrostatic pressure in the second container spaceresulting from a pressure differential defined by a difference betweenthe first liquid surface elevation and the second liquid surfaceelevation; a gas supply line to supply a breathing gas to the secondcontainer space; and an inhalation line having an inhalation inlet inthe second container space and an inhalation outlet outside of theliquid and outside of the second container to provide the breathing gasfrom the second container space to a patient; the second container spaceincreasing in size with an increase in the breathing gas supplied fromthe gas supply line to the second container space; and the inhalationline being configured to open to permit a flow of the breathing gas fromthe inhalation inlet in the second container space to the inhalationoutlet coupled to the patient, causing the second container space todecrease in size.
 2. The ventilator of claim 1, wherein the secondcontainer space increases in size with an increase in the breathing gassupplied from the gas supply line to the second container space,lowering the second liquid surface elevation and raising the firstliquid surface elevation; and wherein the inhalation line is configuredto open to permit the flow of the breathing gas from the inhalationinlet in the second container space to the inhalation outlet coupled tothe patient, causing the second container space to decrease in size,raising the second liquid surface elevation and lowering the firstliquid surface elevation.
 3. The ventilator of claim 2, wherein thefirst container is an outer container having a closed bottom; andwherein the second container is an inverted container having a closedtop and an open bottom, the open bottom of the inverted container beingsubmerged in the liquid of the outer container to provide the secondliquid surface at the second liquid surface elevation inside theinverted container and the first liquid surface at the first liquidsurface elevation between the inverted container and the outercontainer, the inverted container including an inverted container wallsurrounded by an outer container wall of the outer container, the openbottom of the inverted container being spaced from the closed bottom ofthe outer container by an elevation, the inverted container having thesecond container space between the closed top and the second liquidsurface at the second liquid surface elevation.
 4. The ventilator ofclaim 2, wherein the first container and the second container are spacedapart from one another with no overlap and are connected via a fluidconduit through which the liquid flows between the first container andthe second container.
 5. The ventilator of claim 2, wherein the firstcontainer is an outer container having a closed bottom; and wherein thesecond container is an inverted container having a closed top and anopen bottom, the open bottom of the inverted container being submergedin the liquid of the outer container to provide the second liquidsurface at the second liquid surface elevation inside the invertedcontainer and the first liquid surface at the first liquid surfaceelevation between the inverted container and the outer container, theinverted container including an inverted container wall surrounded by anouter container wall of the outer container, the open bottom of theinverted container being spaced from the closed bottom of the outercontainer by an elevation, the inverted container having an invertedcontainer space between the closed top and the second liquid surface atthe second liquid surface elevation; the inverted container beingconfigured to move upward from a first elevation position when thebreathing gas in the second container space reaches a thresholdhydrostatic pressure and to continue moving upward while a volume of theinverted container space increases, the inverted container beingconfigured to stop moving upward and the gas supply line beingconfigured to stop supplying the breathing gas to the inverted containerspace when the inverted container reaches a second elevation position;and the inhalation line being configured to open to permit the flow ofthe breathing gas from the inhalation inlet in the second containerspace to the inhalation outlet coupled to the patient, causing thesecond container space to decrease in size and lowering the elevation ofthe inverted container.
 6. The ventilator of claim 5, furthercomprising: a spring biasing the inverted container in a directionopposing lowering of the elevation of the inverted container.
 7. Theventilator of claim 5, further comprising: a spring in compressionbiasing the inverted container in a direction opposing lowering of theelevation of the inverted container until the inverted container risesabove the spring after the spring is free from compression and is freefrom biasing by the spring.
 8. The ventilator of claim 1, wherein thehydrostatic pressure in the second container space is variable from aninhalation start time when the breathing gas flows from the inhalationinlet in the second container space to the inhalation outlet coupled tothe patient to an inhalation end time when the breathing gas stopsflowing from the inhalation inlet in the second container space to theinhalation outlet.
 9. The ventilator of claim 1, wherein the inhalationline is configured to close and the gas supply line is configured tosupply the breathing gas to the second container space when thehydrostatic pressure in the second container space drops to a basehydrostatic pressure.
 10. The ventilator of claim 9, wherein theinhalation line is configured to open to permit the flow of thebreathing gas from the inhalation inlet in the second container space tothe inhalation outlet coupled to the patient, based on one of (1)detection of a patient breath demand signal or (2) a first presettiming.
 11. The ventilator of claim 10, further comprising: anexhalation line having an exhalation inlet to receive exhaled gas fromthe patient and an exhalation outlet disposed in the liquid in the firstcontainer and outside the second container.
 12. The ventilator of claim11, wherein when the hydrostatic pressure in the second container spacehas dropped to the base hydrostatic pressure, the exhalation line isopened to permit an exhalation gas flow from the patient through theexhalation inlet to the exhalation outlet disposed in the liquid in thefirst container and outside the second container, and the gas supplyline supplies the breathing gas to flow to the second container space.13. The ventilator of claim 12, further comprising: an inhalation sensorcoupled with the inhalation line to detect the patient breath demandsignal.
 14. The ventilator of claim 1, comprising a plurality of secondcontainers in fluidic communication with the first container via theliquid and each having a respective second liquid surface at arespective second liquid surface elevation of the liquid, each secondcontainer including a respective second container space surrounded by arespective second container and the respective second liquid surface,and a respective hydrostatic pressure in the respective second containerspace resulting from a pressure differential defined by a differencebetween the first liquid surface elevation and the respective secondliquid surface elevation; the gas supply line configured to supply thebreathing gas to respective second container spaces of the plurality ofsecond containers; the inhalation line having respective inhalationinlets in the respective second container spaces and an inhalationoutlet outside of the liquid and outside of the plurality of secondcontainers to provide the breathing gas from the respective secondcontainer spaces to the patient; the respective second container spacesincreasing in size with an increase in the breathing gas supplied fromthe gas supply line to the respective second container spaces; and therespective inhalation line being configured to open to permit the flowof the breathing gas from the respective inhalation inlets in therespective second container spaces to the inhalation outlet coupled tothe patient, causing the respective second container spaces to decreasein size.
 15. The ventilator of claim 14, further comprising: a pluralityof valves to control supply of the breathing gas from the gas supplyline to the respective second container spaces and to control the flowof the breathing gas from the respective inhalation inlets in therespective second container spaces to the inhalation outlet coupled tothe patient.
 16. A method of supporting breathing of a patient, themethod comprising: placing a first container and a second containercontaining a liquid in fluidic communication with each other via theliquid, the first container having a first liquid surface at a firstliquid surface elevation of the liquid, the second container having asecond liquid surface at a second liquid surface elevation of theliquid, the second container including a second container spacesurrounded by the second container and the second liquid surface, and ahydrostatic pressure in the second container space resulting from apressure differential defined by a difference between the first liquidsurface elevation and the second liquid surface elevation; supplying abreathing gas via a gas supply line to the second container space, thesecond container space increasing in size with an increase in thebreathing gas supplied from the gas supply line to the second containerspace; placing an inhalation line having an inhalation inlet in thesecond container space and an inhalation outlet outside of the liquidand outside of the second container to provide the breathing gas fromthe second container space to a patient; and opening the inhalation lineto permit a flow of the breathing gas from the inhalation inlet in thesecond container space to the inhalation outlet coupled to the patient,causing the second container space to decrease in size.
 17. The methodof claim 16, wherein the second container space increasing in size, withan increase in the breathing gas supplied from the gas supply line tothe second container space, lowers the second liquid surface elevationand raises the first liquid surface elevation; and wherein opening theinhalation line, to permit the flow of the breathing gas from theinhalation inlet in the second container space to the inhalation outletcoupled to the patient, causes the second container space to decrease insize, raising the second liquid surface elevation and lowering the firstliquid surface elevation.
 18. The method of claim 16, wherein thehydrostatic pressure in the second container space is variable from aninhalation start time when the breathing gas flows from the inhalationinlet in the second container space to the inhalation outlet coupled tothe patient to an inhalation end time when the breathing gas stopsflowing from the inhalation inlet in the second container space to theinhalation outlet.
 19. The method of claim 16, further comprising:closing the inhalation line and supplying the breathing gas via the gassupply line to the second container space when the hydrostatic pressurein the second container space drops to a base hydrostatic pressure. 20.The method of claim 19, further comprising: opening the inhalation lineto permit the flow of the breathing gas from the inhalation inlet in thesecond container space to the inhalation outlet coupled to the patient,based on one of (1) detection of a patient breath demand signal or (2) afirst preset timing.
 21. The method of claim 20, further comprising:placing an exhalation line having an exhalation inlet to receive exhaledgas from the patient and an exhalation outlet disposed in the liquid inthe first container and outside the second container.
 22. The method ofclaim 21, further comprising: when the hydrostatic pressure in thesecond container space has dropped to the base hydrostatic pressure,opening the exhalation line to permit an exhalation gas flow from thepatient through the exhalation inlet to the exhalation outlet disposedin the liquid in the first container and outside the second container,and supplying the breathing gas via the gas supply line to the secondcontainer space.
 23. The method of claim 22, further comprising:detecting the patient breath demand signal using an inhalation sensorcoupled with the inhalation line; and detecting when the hydrostaticpressure in the second container space has dropped to the basehydrostatic pressure using a hydrostatic pressure sensor.
 24. The methodof claim 16, further comprising: placing the first container in fluidiccommunication with a plurality of second containers via the liquid, eachrespective second container having a respective second liquid surface ata respective second liquid surface elevation of the liquid, eachrespective second container including a respective second containerspace surrounded by the respective second container and the respectivesecond liquid surface, and a respective hydrostatic pressure in eachrespective second container space resulting from a pressure differentialdefined by a difference between the first liquid surface elevation andthe respective second liquid surface elevation; supplying the breathinggas via the gas supply line to the respective second container spaces,the respective second container spaces increasing in size with theincrease in the breathing gas supplied from the gas supply line to therespective second container spaces; placing the inhalation line havingrespective inhalation inlets in the respective second container spacesand the inhalation outlet outside of the liquid and outside of theplurality of second containers to provide the breathing gas from therespective second container spaces to a patient; and opening theinhalation line to permit the flow of the breathing gas from therespective inhalation inlets in the respective second container spacesto the inhalation outlet coupled to the patient, causing the respectivesecond container spaces to decrease in size.
 25. The method of claim 24,further comprising: providing a plurality of valves to control supply ofthe breathing gas from the gas supply line to the respective secondcontainer spaces and to control the flow of the breathing gas from therespective inhalation inlets in the respective second container spacesto the inhalation outlet coupled to the patient.
 26. A ventilatorcomprising: a first container and a second container containing a liquidand being in fluidic communication with each other via the liquid, thefirst container having a first liquid surface at a first liquid surfaceelevation of the liquid, the second container having a second liquidsurface at a second liquid surface elevation of the liquid, the secondcontainer including a second container space surrounded by the secondcontainer and the second liquid surface, and a hydrostatic pressure inthe second container space resulting from a pressure differentialdefined by a difference between the first liquid surface elevation andthe second liquid surface elevation; an inhalation line having aninhalation inlet in the second container space and an inhalation outletoutside of the liquid and outside of the second container to provide abreathing gas from the second container space to a patient; and meansfor expanding the second container space by directing the breathing gasfrom a gas supply line to the second container space and contracting thesecond container space by permitting a flow of the breathing gas fromthe inhalation inlet in the second container space to the inhalationoutlet coupled to the patient.
 27. The ventilator of claim 26, whereinthe hydrostatic pressure in the second container space is variable froman inhalation start time when the breathing gas flows from theinhalation inlet in the second container space to the inhalation outletcoupled to the patient to an inhalation end time when the breathing gasstops flowing from the inhalation inlet in the second container space tothe inhalation outlet.
 28. The ventilator of claim 26, wherein theinhalation line is configured to close and the gas supply line isconfigured to supply the breathing gas to the second container spacewhen the hydrostatic pressure in the second container space drops to abase hydrostatic pressure.
 29. The ventilator of claim 28, wherein theinhalation line is configured to open to permit the flow of thebreathing gas from the inhalation inlet in the second container space tothe inhalation outlet coupled to the patient, based on one of (1)detection of a patient breath demand signal or (2) a first presettiming.
 30. The ventilator of claim 29, further comprising: anexhalation line having an exhalation inlet to receive exhaled gas fromthe patient and an exhalation outlet disposed in the liquid in the firstcontainer and outside the second container; wherein when the hydrostaticpressure in the second container space has dropped to the basehydrostatic pressure, the exhalation line is opened to permit anexhalation gas flow from the patient through the exhalation inlet to theexhalation outlet disposed in the liquid in the first container andoutside the second container, and the gas supply line supplies thebreathing gas to flow to the second container space.